chore: merge master into feat/issue-646-policy-guardrail-visibility (base sync)

docs/webui-local-dev.md

@@ -52,7 +52,8 @@ status, onboarding checklist state, and the fail-closed error payloads (#635).
 | Path | Description |
 |------|-------------|
 | `/` | Home / operator overview |
-| `/health` | JSON liveness (`status`, `service`, `mode`, `timestamp`) |
+| `/health` | JSON liveness (`status`, `service`, `mode`, `timestamp`, `uptime_seconds`) |
+| `/api/v1/system/health` | Structured read-only system health (#634) |
 | `/queue` | Live PR and issue queue dashboard (#429) |
 | `/api/queue` | JSON queue export with pagination metadata |
 | `/projects` | Project registry list with status and onboarding progress (#427, #635) |
@@ -80,6 +81,85 @@ Most routes are GET-only. POST/PUT/PATCH/DELETE return `405` with
 `read-only-mvp`, except `/audit` and `/api/audit` which accept POST for
 local validator preview only (no Gitea mutations, no server-side storage).
 
+## System health API (#634)
+
+`GET /api/v1/system/health` is the structured, read-only health surface for
+automated readiness checks. It is the first console API under the `/api/v1`
+prefix; the unversioned MVP exports remain as compatibility aliases.
+
+`/health` is unchanged for existing consumers — every MVP key is still present
+— and now also carries `started_at`, `uptime_seconds`, and a
+`system_health_api` pointer. It stays deliberately cheap and runs no dependency
+probe, because answering readiness costs real work.
+
+**Status codes.** `200` when ready, `503` when a required dependency failed or
+was never probed. Automation can branch on the code without parsing the body.
+
+**Query flags.** The Gitea check is a network call, so it is opt-in:
+`GET /api/v1/system/health?deep=1` runs it and caches the result for
+`WEBUI_HEALTH_PROBE_TTL_SECONDS` (default 15s) so dashboard polling does not
+amplify into remote load. Without the flag that probe reports `skipped`.
+
+**Dependencies.** `control_plane_db` and `repository` are required and drive
+readiness. `gitea` is optional: when it fails the overall `status` degrades but
+`readiness.ready` stays true, because local inventory is still serveable. Each
+entry carries `status`, `detail`, `required`, and `latency_ms`.
+
+Two honesty rules are worth knowing before reading the payload:
+
+* `stale_runtime.mutation_safe` is true only when the runtime, checkout, and
+  remote-tracking commits are all known and equal. An unfetched remote is
+  reported as indeterminate, never as safe.
+* `mcp_namespaces` entries are always `unproven`. A web process runs outside
+  the IDE-managed MCP client and cannot invoke a namespace tool, so per #543
+  only a `client_namespace` probe can prove that path.
+
+Sample response (abridged, healthy):
+
+```json
+{
+  "status": "ok",
+  "service": "mcp-control-plane-webui",
+  "mode": "read-only",
+  "api": "/api/v1/system/health",
+  "timestamp": "2026-07-22T11:04:18.512034+00:00",
+  "readiness": { "ready": true, "complete": true, "reasons": [] },
+  "version": {
+    "git_sha": "620ed6e9a9550b8da2ceb82d9ab8744e8920490f",
+    "git_describe": "v1.1.0-898-g620ed6e",
+    "control_plane_schema_version": 4,
+    "python_version": "3.14.5",
+    "known": true
+  },
+  "process": { "started_at": "2026-07-22T10:58:02.114+00:00", "uptime_seconds": 376.4 },
+  "deep_probes_requested": false,
+  "dependencies": [
+    {
+      "name": "control_plane_db",
+      "kind": "sqlite",
+      "status": "ok",
+      "detail": "schema v4 readable",
+      "required": true,
+      "healthy": true,
+      "latency_ms": 1.482,
+      "metadata": { "schema_version": 4, "active_leases": 3 }
+    },
+    { "name": "repository", "kind": "git", "status": "ok", "required": true, "healthy": true },
+    { "name": "gitea", "kind": "http", "status": "skipped", "required": false, "healthy": false }
+  ],
+  "mcp_namespaces": [
+    { "namespace": "gitea-author", "required_tool": "gitea_whoami", "status": "unproven" }
+  ],
+  "stale_runtime": { "stale": false, "determinable": true, "mutation_safe": true, "reasons": [] },
+  "probe_errors": []
+}
+```
+
+No restart, reload, or process-kill control is exposed here: those are Phase 2
+at the earliest, and #630 forbids process-kill recovery outright. Every probe
+opens its subject read-only — the control-plane database is opened through a
+`mode=ro` URI so a health check can never create or migrate a schema.
+
 ## Report audit (#431)
 
 Paste an LLM final report at `/audit` or POST JSON to `/api/audit`. The UI