feat: Sentry/GlitchTip incident bridge via incident_links (Closes #612)

Add phase-1 observability bridge that turns provider observations into
normal Gitea issues and control-plane incident_links rows. Dry-run is
default; apply creates/links through sanctioned Gitea issue paths only.
Raw incidents remain non-assignable; the #600 allocator sees bridge work
only as ordinary Gitea issues. Builds on #613 substrate and #600 allocator.

Closes #612

docs/architecture/control-plane-db-substrate.md

@@ -49,12 +49,25 @@ Module: `allocator_service.py` · MCP tool: `gitea_allocate_next_work`
 - `apply=true` reserves via `ControlPlaneDB.assign_and_lease` (atomic assignment+lease).
 - Coordination source is **always** the control-plane DB — not file locks or comment-only leases.
 - Routing follows ADR §5.3 (REQUEST_CHANGES → author, terminal path first, foreign lease → wait).
-- Raw monitoring incidents are never candidates (#612 remains downstream).
+- Raw monitoring incidents are never candidates.
+
+## Incident bridge (#612)
+
+Module: `incident_bridge.py` · MCP tools: `gitea_observability_*`
+
+- Bridge converts Sentry/GlitchTip observations → **normal Gitea issues** + `incident_links`.
+- Phase-1: `gitea_observability_reconcile_incident(apply=false|true)` with JSON observation.
+- Dry-run performs **no** Gitea mutation and **no** DB write.
+- Apply reuses existing links or creates one Gitea issue; never invents `work_items.kind=incident`.
+- Config: `GITEA_OBSERVABILITY_PROJECTS_JSON` or `GITEA_OBSERVABILITY_PROJECTS_FILE`.
+- Provider tokens never appear in issue bodies, links, or tool results.
+- Allocator sees bridge work only after a Gitea issue exists.
 
 ## Non-goals (intentionally deferred)
 
-- Sentry/GlitchTip provider adapters and auto-watchdog — **#612**
-- Gitea comment/label mirror writers (may be added by allocator tooling later)
+- Full unsupervised watchdog auto-filing (prefer explicit reconcile first)
+- Assuming GlitchTip writeback API equals Sentry without verification
+- Gitea comment/label mirror writers for every assignment (optional later)
 
 ## Tests