feat: container monitoring backend core (PR-1)

- Add instance_events and health_checks tables with Alembic migration
- InstanceEventBus: typed pub/sub singleton with wildcard support
- HealthMonitor: async background loop polling containers every 15s
- SSE endpoint GET /events/stream with auth and connection limits
- Lifecycle hooks in tool_instances.py (create/start/stop/restart/delete)
- Structured JSON logging with correlation IDs
- 15 new unit tests (EventBus, HealthMonitor, MonitoringModels)

Quality gates: pytest 15 new passed, ruff clean

.atl/.skill-registry.cache.json

@@ -1,3 +1,3 @@
 {
-  "fingerprint": "c324de9e9faf30231900c691aca5f3a07c7db099"
+  "fingerprint": "fdea8a74bb4c7449c01c4bd61646c895b10ede78"
 }

.atl/skill-registry.md

@@ -2,11 +2,12 @@
 
 <!-- Auto-generated by gentle-pi extensions/skill-registry.ts. Run /skill-registry:refresh to regenerate. -->
 
-Last updated: 2026-05-27
+Last updated: 2026-05-28
 
 ## Sources scanned
 
 - .opencode/skills
+- .claude/skills
 - /home/alex/.config/opencode/skills
 
 ## Contract
@@ -25,6 +26,7 @@ Last updated: 2026-05-27
 | `openspec-archive-change` | Archive a completed change in the experimental workflow. Use when the user wants to finalize and archive a change after implementation is complete. | project | `/home/alex/projects/headquarter/.opencode/skills/openspec-archive-change/SKILL.md` |
 | `openspec-explore` | Enter explore mode - a thinking partner for exploring ideas, investigating problems, and clarifying requirements. Use when the user wants to think through something before or during a change. | project | `/home/alex/projects/headquarter/.opencode/skills/openspec-explore/SKILL.md` |
 | `openspec-propose` | Propose a new change with all artifacts generated in one step. Use when the user wants to quickly describe what they want to build and get a complete proposal with design, specs, and tasks ready for implementation. | project | `/home/alex/projects/headquarter/.opencode/skills/openspec-propose/SKILL.md` |
+| `sift-backlog` | Triage and organize backlog tasks into actionable plans. Use when asked to review the backlog, prioritize tasks, create plans from backlog items, or move tasks from backlog to open status. Handles the full workflow of listing backlog tasks, grouping related tasks into plans, setting priorities and dependencies, activating plans, and changing task status from backlog to open. | project | `/home/alex/projects/headquarter/.claude/skills/sift-backlog/SKILL.md` |
 
 ## Loading protocol