refactor(service-messaging): migrate isUniqueViolation onto the shared @objectstack/types predicate (#6542)

[os-project-manager]

Closes #6542

What

Migrates service-messaging off its private hand-written isUniqueViolation() (the last of the four copies #6250 inventoried, and the one the shared predicate was seeded from) onto isUniqueViolationError from @objectstack/types (landed in PR #6541).

• packages/services/service-messaging/src/messaging-service.ts — import swap at the single call site (the inbox read-receipt check-then-act race fallback in upsertReadReceipt), local function deleted.
• packages/services/service-messaging/package.json — the card said the dep was already present; re-verification showed it was NOT, so @objectstack/types (workspace) is added here, with the lockfile entry. This is the one deviation from the card's premise, and it was declared in scope by dispatch for exactly this case.

The one behaviour change, tested at the call site

The shared predicate additionally follows a bounded number of steps down the cause chain (pool and query-builder layers wrap the driver error). The old copy read only the top-level code/message, judged a wrapped conflict "not a conflict", and rethrew — markRead logged the failure, reported readCount: 0, and the receipt stayed delivered. Now the wrapped conflict triggers the flipToRead() convergence, same as a bare driver error. That is the direction the call site wants: a wrapped conflict is still a conflict.

Tests added in messaging-service.test.ts:

• Wrapped conflict (new behaviour): a wrapper whose own text matches none of the predicate's signals, carrying the Postgres conflict as cause, exercised through the real markRead → upsertReadReceipt path; asserts readCount: 1 and convergence to the concurrent row.
• Unwrapped three-dialect pin (unchanged behaviour): it.each over plain Postgres (23505), MySQL (ER_DUP_ENTRY/errno 1062), and SQLite (UNIQUE constraint failed) error shapes through the same path — each converges identically to before.

Reverse verification (direction decided beforehand)

With the old local predicate temporarily restored at the call site: exactly the wrapped-conflict test goes red (1 failed) and the three dialect pins plus the rest of the file stay green (51 passed). Restored, all green.

Verification

• pnpm --filter '@objectstack/service-messaging' test — 16 files, 199 passed, 0 failed (main had 195; +4 new).
• pnpm --filter '@objectstack/service-messaging' typecheck — clean.
• npx eslint on both touched source files — exit 0.
• node scripts/check-nul-bytes.mjs — OK.

Changeset: .changeset/messaging-shared-unique-violation-predicate.md (patch, @objectstack/service-messaging).

🤖 Generated with Claude Code

https://claude.ai/code/session_01USNUyHEr7uaU6MoEWXitei

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
objectstack	Ignored		Aug 8, 2026 7:25am

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📓 Docs Drift Check

This PR changes 1 package(s): @objectstack/service-messaging.

4 hand-written doc(s) reference the affected code and may need an implementation-accuracy re-verification:

• content/docs/automation/webhooks.mdx (via @objectstack/service-messaging)
• content/docs/kernel/services-checklist.mdx (via @objectstack/service-messaging)
• content/docs/plugins/packages.mdx (via @objectstack/service-messaging)
• content/docs/releases/implementation-status.mdx (via @objectstack/service-messaging)

Advisory only. To re-verify, run the docs-accuracy-audit workflow scoped to these files:
node scripts/docs-audit/affected-docs.mjs origin/main → pass the list as args.docs.