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/test/fixtures/crash-script.ts

@@ -0,0 +1,18 @@
+import type { FakeScript } from "../../src";
+
+export const RUN_ID = "run-crash-1";
+
+export const crashScript: FakeScript = {
+  match: "Dune",
+  steps: [
+    { text: "先查库存。", toolCalls: [{ capability: "inventory.query", input: { title: "Dune" } }] },
+    {
+      text: "库里没有,提交下载。",
+      toolCalls: [{ capability: "download.submit", input: { title: "Dune", quality: "1080p" } }],
+    },
+  ],
+  finalText: (results) => {
+    const last = results.at(-1);
+    return last?.isError ? `下载提交结果未知,需要核对:${last.text.slice(0, 40)}` : "已提交(未入库)";
+  },
+};