feat(metrics): add phase-0 baseline counters

Diagrams reviewed: docs/architecture/AGENT_DIAGRAM.md, docs/architecture/GATEWAY_SESSIONS_AND_QUEUE.md, docs/api/PROTOCOL.md (no changes required).

docs/plans/2026-02-25-phase0-instrumentation-ticket-checklist.md

@@ -90,6 +90,8 @@ Emit new audit events without changing request handling behavior:
 
 ## Ticket 0.3 — Metrics Collector Baseline Counters
 
+Status: completed (2026-02-25)
+
 ### Scope
 
 Extend in-memory gateway metrics with baseline counters:

docs/plans/state.json

@@ -32,6 +32,22 @@
       ],
       "test_status": "pnpm test:run src/daemon/routing.test.ts + pnpm test:run src/gateway/handlers/agent.test.ts passing"
     },
+    "phase0-ticket-0.3-metrics-baseline-counters": {
+      "status": "completed",
+      "date": "2026-02-25",
+      "updated": "2026-02-25",
+      "summary": "Implemented Phase 0 Ticket 0.3 by adding run-state counters, cancel-latency samples, and reaction decision counters to gateway metrics with routing/gateway emitters to populate the new baselines.",
+      "files_modified": [
+        "src/gateway/metrics.ts",
+        "src/gateway/metrics.test.ts",
+        "src/gateway/handlers/agent.ts",
+        "src/daemon/routing.ts",
+        "src/daemon/index.ts",
+        "docs/plans/2026-02-25-phase0-instrumentation-ticket-checklist.md",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/gateway/metrics.test.ts src/daemon/routing.test.ts src/gateway/handlers/agent.test.ts passing"
+    },
     "phase0-instrumentation-ticket-checklist": {
       "status": "completed",
       "date": "2026-02-25",
@@ -6644,7 +6660,8 @@
     "deeper_surfaces_phase0_ticket_pack": "completed — produced an atomic implementation checklist for Phase 0 baseline observability work (audit events, router/gateway emitters, metrics counters, baseline summary tooling, docs sync)",
     "deeper_surfaces_phase0_ticket_01": "completed — audit schema/logger now capture run lifecycle and reaction decision baseline events (`run.state`, `run.cancel`, `reaction.match`, `reaction.skip`) with regression test coverage",
     "deeper_surfaces_phase0_ticket_02": "completed — gateway + daemon routing emit run lifecycle/cancel telemetry and reaction match/skip audit events with filter summaries and cancellation latency, plus focused tests",
-    "next_up": "Implement Ticket 0.3 from docs/plans/2026-02-25-phase0-instrumentation-ticket-checklist.md",
+    "deeper_surfaces_phase0_ticket_03": "completed — gateway metrics now track run-state outcomes, cancel latency samples, and reaction decision counters with routing/gateway emitters",
+    "next_up": "Implement Ticket 0.4 from docs/plans/2026-02-25-phase0-instrumentation-ticket-checklist.md",
     "pi_embedded_canary_spike": "completed — added optional pi_embedded backend adapter, canary-safe no-tools routing guard, backend success/fallback latency audit events, and docs/diagram updates while native remains default",
     "pi_embedded_evaluation_phase": "completed — final decision rollback (applied in runtime config): Window A failed latency/fallback gates (p50 +259ms, p95 +5695ms, fallback 25%, categories: pi_module_interface/empty_assistant_text); Window B remained sample-insufficient; controlled probes verified guard coverage (pi_no_tools_mode/capability_query/attachments_present each hit once)",
     "pi_embedded_manual_mode": "completed — added persisted runtime backend controls for manual Pi activation/deactivation (`/runtime` preferred, `/backend` alias; `status`, `activate pi`, `deactivate pi`, `use config`) while keeping config-driven default routing",