feat(agent): capability registry, Pi AgentRuntimePort, fake model provider and redaction guard (W1-5)

- CapabilityRegistry: descriptor(id/version/schema/scope/risk/idempotent/preview/replay),
  invoke = scope limit -> input schema -> server-side authorize -> idempotency key -> handler
  -> output schema -> audit; capability id <-> tool name mapping (download.submit <-> download__submit)
- PiAgentRuntime (pi-agent-core AgentHarness 0.87.1): whitelist tools + before_tool re-check,
  redacted event stream, JSONL session at sessionDir/<runId>.jsonl, resume/abort/compact,
  tool-call/duration/token/cost budgets -> abort + run_failed(budget)
- AgentSettings -> pi-ai createProvider (anthropic / openai-compatible), compaction mapping
- FakeModelProvider + createFakeRuntime (scripted, transcript-derived, survives crash/resume)
- buildSystemPrompt, redactForModel; 27 tests incl. SIGKILL + resume

Co-Authored-By: Claude Fable 5.1 <[email protected]>

packages/agent/package.json

@@ -9,5 +9,12 @@
   "scripts": {
     "typecheck": "tsc -p tsconfig.json",
     "test": "vitest run"
+  },
+  "dependencies": {
+    "@earendil-works/pi-agent-core": "0.87.1",
+    "@earendil-works/pi-ai": "0.87.1",
+    "@umt/contracts": "workspace:*",
+    "typebox": "1.3.27",
+    "zod": "^4.6.5"
   }
 }