docs(state): record Batch 4 completion

PROJECT_STATE.md

@@ -426,3 +426,37 @@ any change at `docs/functional-completion/server-baseline.md`.
 - Deployed to Unraid and re-verified against the live server; demo data reset afterward.
 - Exact next action: Batch 4 — global search backend + UI, demo reset UI trigger,
   truthful aggregate integration status (n8n/RAGcore/MCP).
+
+### Batch 4 — complete (commits `4437b87`, `1867828`)
+
+- Added `GET /api/v1/search` — bounded typed results (vehicle/booking/data-quality-issue/
+  section), role-filtered server-side (data-quality and manager-only sections excluded
+  for Rental Employee), customers never returned (no customer detail route exists).
+  Replaced `Layout.tsx`'s blind client-side regex/term guesser with a debounced
+  (250 ms) call to this endpoint, a real `role="listbox"` results panel, arrow-key
+  navigation, Enter/Escape, outside-click close, and a no-results state.
+- Added `GET /api/v1/integrations/status`, aggregating outbox delivery counts into one
+  truthful n8n state (`disabled`/`unavailable`/`degraded`/`operational`/`no_evidence`)
+  instead of the dashboard/automation cards showing whichever status the single most
+  recent event happened to be in. Wired into both `Automation.tsx` and `Dashboard.tsx`.
+  MCP Hub card now reflects the real `registration_enabled` setting.
+- Found and fixed a real config gap this surfaced: `MCP_HUB_REGISTRATION_ENABLED` was
+  documented in `.env.example` but had no `Settings` field, so it was silently dropped
+  by `extra="ignore"` and never read anywhere in the codebase.
+- Added a "Reset demo data" action to the sidebar (Operations Manager only, confirm,
+  progress, error handling) — the endpoint already existed and was already gated, just
+  had no UI trigger. Reset invalidates the acting session server-side, so the flow signs
+  the user out and returns to login.
+- New regression coverage: backend — search role-filtering/customer-exclusion/no-match,
+  integration-status role-gate and state-derivation (including a test that resolves all
+  seeded failures and asserts the state flips to `operational`). Frontend — vehicle/
+  booking/data-quality-issue search navigation, keyboard nav, no-results + Escape, demo
+  reset happy path, rental employee cannot see the reset button, automation page shows
+  aggregate counts.
+- Local evidence: `pytest` 109 passed, `ruff check .` clean, `mypy app` 0 issues/46 files,
+  `npx tsc -b` clean, `npm run build` clean, `npx playwright test` **37 passed**, stable
+  across two repeated full-suite runs.
+- Deployed to Unraid and re-verified against the live server; demo data reset afterward.
+- Exact next action: Batch 5 — bounded outbox delivery-lease recovery for stale
+  `delivering` events, a second (scheduled quality-scan) n8n workflow, final
+  documentation/contract updates and acceptance evidence.