feat(storage): name the missing-tenant-schema error so callers can branch on it

[guangyu-reflexio]

Why

handle_exceptions collapses every driver exception into an anonymous
StorageError carrying a formatted message, which erases the exception class.
That is fine for the general case, but it leaves one condition unrecoverable at
the caller: this org's tenant schema does not exist.

The rendered text is InvalidSchemaName: schema "org_N" does not exist, which
matches neither isinstance(exc, psycopg2.errors.InvalidSchemaName) (the type is
gone) nor an "invalid schema" substring — there is no space in the class name.
So a caller that wants to treat a vanished tenant differently from a transient
fault has nothing to branch on.

The enterprise side needs exactly that: a background sweep must park an org
whose schema is gone rather than re-querying it every few minutes. Without a
type to key on, its only options are a bare except Exception — which would
suspend a healthy tenant's work on a transient blip — or substring-matching a
formatted message.

What

Adds TenantSchemaMissingError(StorageError), following the existing
UserPlaybookRetentionHoldActiveError precedent: classify at raise time and hand
the caller a name.

It is a subclass, so every existing except StorageError handler is
unaffected. This narrows the type, it does not change the contract.

This is a classification, not a softening — a missing schema for a verified org
is a real provisioning failure and still logs at ERROR.

Verification

5040 passed, 10 skipped (unit tier), coverage 76.95%.

Summary by CodeRabbit

• Bug Fixes
  • Improved error reporting for cases where a tenant schema is missing or unavailable.
  • Preserved the specific schema-related error after storage driver errors are processed.

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 56fd02a and 9825afd.

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• reflexio/server/services/storage/error.py

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📝 Walkthrough

Walkthrough

Changes

Tenant schema error classification

Layer / File(s)	Summary
Tenant schema error contract reflexio/server/services/storage/error.py	Adds the public TenantSchemaMissingError class as a StorageError subclass for missing or unexposed tenant schemas.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Feature

Merge Risk: ⚪ Minimal · up to 9825a

The change adds a typed storage error while preserving existing StorageError compatibility, with no identified merge-blocking impact.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding a named error for missing tenant schemas so callers can branch on it.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 1 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/tenant-schema-missing-error

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