fix: dashboard Overview stats render a blank box on a fresh archive — show zeros instead

[rorybyrne]

Observed

On a freshly deployed archive with no conventions yet, the archive overview's What's in here → Overview panel renders a blank card: the "Overview" label with nothing under it. The adjacent "By record type" panel handles this state correctly ("No datasets yet" empty state); Overview just goes blank.

Expected

A zero-state stat row, not an empty box:

• Published records 0
• Derived features 0 per record
• Stored MB

A brand-new archive already serves exactly this — GET /api/v1/stats on a fresh instance returns 200:

{"records":0,"records_this_month":0,"storage_bytes":122880,"features_per_record":0.0,"computed_at":"…","data_url":"/api/v1/data"}

so the data layer supports rendering zeros today; only the panel's render path loses it.

Where

apps/dashboard/src/features/tenant-insights/WhatsInHere.tsx:

{stats.isPending ? (
  <Skeleton height="6rem" width="100%" />
) : stats.data ? (
  <div className={styles.statRow}>…</div>
) : null}

The : null arm means any non-pending state without data — a failed fetch through the proxy, a decode failure in decodeRecordStats — renders an empty card. The query's error state is swallowed entirely: "stats are zero", "stats failed to load", and "endpoint not reachable yet" are all indistinguishable blanks.

Suggested fix

1. When the stats query resolves, always render the stat row — zeros included (this is the current happy path once the fetch succeeds, so the visible blank implies the error arm; fixing only the copy is not enough).
2. Replace the null arm with an explicit state: either a retryable "Couldn't load stats" note, or a zero-valued stat row with a subtle "unavailable" treatment — anything but a silently empty card.
3. Give Overview the same courtesy "By record type" already has: a deliberate empty/zero state designed for the first-run experience, since a new archive owner lands here before their first convention deploy.

Acceptance

• Fresh archive (no conventions, no records): Overview shows 0 / 0 per record / <n> MB, never a blank card.
• Stats endpoint erroring: Overview shows an explicit failure state (distinguishable from zeros), never a blank card.