feat(settings): nested settings directory with a per-tenant registry

AGENTS.md

@@ -29,7 +29,7 @@ One binary:
 Eighteen internal packages under `internal/` (plus `internal/testutil/` for shared test helpers):
 
 - **`api/`** — Chi HTTP router, JWT/JWKS middleware (from `auth/`), ingest/query/structured-query/SSE/schema/DLQ/pipes handlers
-- **`app/`** — the process wiring: `New` builds every component from the boot config and the settings directory (each one wired in one place — what it opens, what it loops, what it releases — with the settings store handed to its wiring function whole, the injection point of the per-tenant registry of #583: store-keyed getters for the handlers, `perTenant` for the async paths), `Run` drives the long-lived ones under one `errgroup` until the context is cancelled or one fails, `Close` releases them in reverse order. `cmd/wavehouse` and `tests/integration` both boot through it
+- **`app/`** — the process wiring: `New` builds every component from the boot config and the settings directory (each one wired in one place — what it opens, what it loops, what it releases — with the settings registry handed to its wiring function whole, the injection point of the per-tenant registry of #583: store-keyed getters for the handlers, `perTenant` for the async paths, and `defaultSetting`/`onDefaultAdopt` for the resources a process still has one of, which follow tenant `0`), `Run` drives the long-lived ones under one `errgroup` until the context is cancelled or one fails, `Close` releases them in reverse order. `cmd/wavehouse` and `tests/integration` both boot through it
 - **`auth/`** — JWT auth middleware: HMAC **or** JWKS verification with `alg` pinned to the active verifier, role extraction from a configurable claim path; always runs, never rejects (bad token → empty role + stashed reason)
 - **`cache/`** — `Cache` interface → `LocalCache` (Ristretto) + `SharedCache` (TBD) + `TieredCache` (singleflight)
 - **`chconn/`** — `Manager`, the one ClickHouse `driver.Conn` every consumer holds; `Reconfigure` swaps the connection behind it after a settings reload changes the wiring (never dials; the old connection closes after a `query_timeout` grace)
@@ -43,9 +43,9 @@ Eighteen internal packages under `internal/` (plus `internal/testutil/` for shar
 - **`pipes/`** — Named query pipes: `NamedQuery` type + `BindParams` + `Source` (read per request; `settings.Store` in production, `Static(q...)` in tests)
 - **`policy/`** — Hasura-style access control, **role-first**: `TablePolicy` is `map[string]RolePermissions`, and a role's grant splits by operation into `SelectPermissions` (columns, row `filter`, aggregations, the `max_*` limits) and `InsertPermissions` (columns, `check`) — so a field only one side honors does not exist on the other. `Evaluate()` resolves ONE operation and leaves the other side **nil** (`Select *ResolvedSelect` / `Insert *ResolvedInsert`), which every accessor fails closed on — nil is "not resolved", distinct from an empty side, which is "unrestricted" (what the admin return builds). Claim templating (`{{ jwt.claim.path }}`) resolves during that call. Policies come from `Source`, a `func() *Policy` read per call (`settings.Store.Policy` in production, `Static(p)` in tests)
 - **`query/`** — Structured query AST types + SQL builder with schema validation, structural policy predicate/limit emission, timestamp bucketing
-- **`settings/`** — the settings directory: `Validate` (strict JSON, per-file rules, cross-file role references), `Store` (the adopted snapshot + serialized `Reload`, typed accessors read per call, `AfterAdopt` hooks), `Registry` (tenant id → `Store`; holds the one store under `tenant.Default`), the fsnotify `Watch`, and the embedded (`go:embed`) seed `wavehouse bootstrap` writes
+- **`settings/`** — the settings directory, in either shape ([#583](https://github.com/Wave-RF/WaveHouse/issues/583)): flat (the four files: tenant `0` alone) or nested (one folder per tenant, never mixed). `Validate` detects the shape and checks it — `ValidateDir` per directory (strict JSON, per-file rules, cross-file role references), folder names against `tenant.Parse`, a nested finding's `File` led by its folder; `Store` is a passive holder (one tenant's adopted snapshot, typed accessors read per call); `Registry` (tenant id → `Store`) owns `Open`, the serialized `Reload`/`ReloadTenant`, the `AfterAdopt` hooks, and the fsnotify `Watch` (flat only). Flat refuses an invalid directory at boot and keeps the previous snapshot on a rejected reload; nested fails closed per tenant (a rejected folder stops being served, the rest carry on, a whole-tree reload mirrors the folders, and a finding about the root itself rejects the reload whole). Plus the embedded (`go:embed`) seed `wavehouse bootstrap` writes
 - **`stream/`** — SSE fan-out: rows travel POSITIONALLY, so each connection is told its projected column list in an `event: schema` frame before its first row and again on drift — **not** guaranteed after a gap-fill across a column change, which can leave a connection reading live rows against a stale list until it reconnects ([#543](https://github.com/Wave-RF/WaveHouse/issues/543)) — (tracked per connection; replay tracks its own). The event `Hub` (registers subscribers by `(topic, role)`; `Broadcast` projects + serializes each event once per role, the #294 delivery hot path — a role carrying a row-level `filter` keeps the shared projection but delivers per subscriber, each subscriber's claims evaluated against the row, #319), `Subscriber` (per-connection outbound `Frame` queue, `Send`/`Frames`; claims fixed at construction, immutable), the `Bucket` fan-out set (`subscriberSet`, one per `(topic, role)`), the `Heartbeater` keepalive wheel, and `Metrics` (the `wavehouse_sse_*` stream instruments)
-- **`tenant/`** — the tenant identifier ([#583](https://github.com/Wave-RF/WaveHouse/issues/583)): `ID` (a validated string), `Parse` (letters, digits, `_`, `-`; ≤ 64 bytes — safe as a folder name and as an MQ subject token), `Default` (`"0"`), and `Header` (`X-Tenant-ID`). Imports nothing from the rest of the repo. `api.TenantMW` resolves the header against `settings.Registry` before auth on every `/v1` route outside `/v1/ops/*` (`400` malformed, `404` unknown) and puts the resolved `*settings.Store` in the request context; handlers read it once (`api.StoreFromContext`) and pass it down as an argument, and nothing below a handler reads context. The async paths (ingest worker, sweeper, stream hub, schema registry) are constructed with a `tenant.ID` and their getters take it
+- **`tenant/`** — the tenant identifier ([#583](https://github.com/Wave-RF/WaveHouse/issues/583)): `ID` (a validated string), `Parse` (letters, digits, `_`, `-`; ≤ 64 bytes — safe as a folder name and as an MQ subject token), `Default` (`"0"`), and `Header` (`X-Tenant-ID`). Imports nothing from the rest of the repo. `api.TenantMW` resolves the header against `settings.Registry` before auth on every `/v1` route outside `/v1/ops/*` (`400` malformed, `404` unknown, a bare `503` for a nested tenant whose folder was rejected) and puts the resolved `*settings.Store` in the request context; the ops routes that address one tenant (`GET /v1/ops/pipes[/{name}]`, `POST /v1/ops/settings/reload`) take a strictly parsed `?tenant=` instead; handlers read it once (`api.StoreFromContext`) and pass it down as an argument, and nothing below a handler reads context. The async paths (ingest worker, sweeper, stream hub, schema registry) are constructed with a `tenant.ID` and their getters take it
 
 ## Key Design Decisions
 
@@ -61,7 +61,7 @@ The invariant index — what must stay true. Full narrative and rationale live i
 8. **Optional dedup** — opt-in via `dedupe.enabled` in the settings directory's `config.json` (hot-reloadable: a reload opens or closes the Pebble store via `dedupe.Managed`); `dedupe.id_field` there selects the JSON key, overridable per table.
 9. **Singleflight** — `TieredCache` coalesces concurrent misses (`x/sync/singleflight`) to prevent cache stampede.
 10. **Active Sweeper** — purges NATS messages that are both ACKed (written to CH) and older than the gap window; SSE gap-fill uses `DeliverByStartTime`, no in-process ring buffer.
-11. **Hasura-style access control: fail-closed (security)** — `policy.IsAdmin` (role == `admin_role`, **exact case-sensitive**, default `"admin"`) is the single admin check, shared by `Evaluate`/`ResolveRole`/`Validate`/the `/v1/ops` gate/`RoleAllowed`. Empty/absent role matches nothing (no `"*"` wildcard); `Validate` rejects empty role keys; a `nil` policy (deleted) denies **everyone incl. admin** via a role — a total lockout for token-based callers, so recovery is writing `policies.json` and reloading, never an implicit admin grant (**exception:** the operator key's `auth.IsOperator` bit passes the `/v1/ops` gate even under a `nil` policy — a deliberate break-glass that can `POST /v1/ops/settings/reload` over HTTP, see #7). `default_role` is the one sanctioned roleless exception (`ResolveRole` maps empty → it pre-eval); `default_role == admin_role` is permitted but dev-only and loudly warned (`policy.DefaultRoleGrantsAdmin`). Preserve when touching `internal/policy` (policy twin of #13; see #159). Detail: architecture.md § `policy/`.
+11. **Hasura-style access control: fail-closed (security)** — `policy.IsAdmin` (role == `admin_role`, **exact case-sensitive**, default `"admin"`) is the single admin check, shared by `Evaluate`/`ResolveRole`/`Validate`/the `/v1/ops` gate/`RoleAllowed`. Empty/absent role matches nothing (no `"*"` wildcard); `Validate` rejects empty role keys; a `nil` policy (deleted) denies **everyone incl. admin** via a role — a total lockout for token-based callers, so recovery is writing `policies.json` and reloading, never an implicit admin grant (**exception:** the operator key's `auth.IsOperator` bit passes the `/v1/ops` gate even under a `nil` policy — a deliberate break-glass that can `POST /v1/ops/settings/reload` over HTTP, see #7). Over a nested settings directory the `/v1/ops` gate reads no policy at all — those routes reach every tenant, so the operator key alone passes and an admin-role token gets `403`; `api.NewRouter` decides that from the registry's shape, not from what was wired. `default_role` is the one sanctioned roleless exception (`ResolveRole` maps empty → it pre-eval); `default_role == admin_role` is permitted but dev-only and loudly warned (`policy.DefaultRoleGrantsAdmin`). Preserve when touching `internal/policy` (policy twin of #13; see #159). Detail: architecture.md § `policy/`.
 12. **Structured queries: column authz fail-closed (security)** — `POST /v1/query?table={table}`: typed AST validated against schema, permission-enforced, timestamp-bucketed for cache, `DefaultMaxRows` (10,000) cap. Every column reference — projection, aggregation args, `filters`, `group_by`, `order_by`, `time_range` — is authorized inside `query.Build` (the single chokepoint that enumerates them all), so no clause can skip the role's `allow_columns`/`deny_columns` check (#223). A `select_all` read by a *column-restricted* role expands to its allowed columns via `policy.AllowedProjection`, never a bare `SELECT *`; *unrestricted*/admin roles keep `SELECT *` (`policy.RestrictsColumns` decides). Omitting `columns` selects nothing (`ErrEmptyProjection` → `200 []`); `["*"]` is the literal column `*` (schema-gated, not a wildcard); a table-granted role with no readable columns fails closed (`ErrNoReadableColumns` → `403`). Structured and live-stream (`stream.projectIndices`) reads share the one per-column decision `policy.IsColumnAllowed`, so column visibility can't drift. Row visibility has the same one-source guarantee (#319): `Evaluate` resolves a role's row-`filter` once (`resolvePredicates`), and both surfaces consume that single resolution — the query path renders it to SQL (`predicatesToSQL`), the stream evaluates it in memory per subscriber (`ResolvedPermissions.RowVisible`, whose type-aware comparison fails closed on anything it can't prove about the ingested payload — `policy.ColumnSpec`, with `DateTime`/`DateTime64` operands compared as instants through the ingest grammar (`discovery.Column.TimeParser`) and claim constants rendered canonically and digit-exact by the one shared rule `policy.CanonicalScalar` (#457 — which also refuses a float64 at/past 2^53 rather than match a neighboring ID, and whose ok=false — an absent claim, a structured value, no canonical form — makes the predicate match no rows on BOTH surfaces: `1 = 0` in SQL, every row withheld in memory); numeric comparison runs in the column's STORAGE domain (`policy.NumericSpec`, classified by `discovery.NumericStorageOf` — Float width rounding, Decimal scale truncation, integer exactness, both operands narrowed as ClickHouse narrows stored value and bound constant, out-of-range operands refused rather than modeled; the `tests/integration` differential oracle holds in-range verdicts equal to a live ClickHouse's and the never-admit-where-SQL-hides direction for the refused out-of-range ones); an event whose insert later fails into the DLQ is the one residual payload-vs-stored asymmetry, documented in the access-control enforcement caution) — so row visibility can't drift either. Preserve when touching `internal/query` or the structured-query handler. Detail: architecture.md § `query/`.
 13. **Named query pipes: fail-closed (security)** — pre-defined SQL templates (Tinybird-style) with param binding + caching; `GET/POST /v1/pipes/{name}` sit outside `RequireAdmin`, so per-pipe `allowed_roles` is the *only* execute-path gate, via `policy.RoleAllowed`: exact allowlist membership (no `"*"`), admin always passes, empty/absent role and empty-string entries authorize nobody, and no `allowed_roles` → admin-only. Preserve and exercise via `testutil.RunRoleMatrix` / `StandardRoleMatrix` (see #159). Detail: architecture.md § `pipes/`.
 14. **TypeScript SDK** — `@wavehouse/sdk`: typed query builder, real-time SSE over `fetch`, live queries (incrementable/decomposable/poll aggregation), codegen CLI. Exactly one runtime dependency — `eventsource-parser` (SSE framing, itself dependency-free); adding a second needs the same scrutiny the first got. The canonical client (see §SDK Sync).