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/src/index.ts

@@ -1,2 +1,43 @@
-// @umt/agent 公开入口;W1 起在此导出实现
+// @umt/agent 公开入口。Pi SDK 类型只出现在 src/pi/*,这里只导出本包自有接口。
 export const PACKAGE_NAME = "@umt/agent";
+
+export { CapabilityError, type CapabilityErrorCode, isCapabilityError } from "./capability/errors";
+export {
+  CapabilityRegistry,
+  type CapabilityRegistryOptions,
+  defaultIdempotencyKey,
+  type RegisteredCapability,
+  stableStringify,
+} from "./capability/registry";
+export { capabilityIdToToolName, isCapabilityId, toolNameToCapabilityId } from "./capability/tool-name";
+export * from "./capability/types";
+export {
+  type CreateFakeRuntimeOptions,
+  createFakeRuntime,
+  FAKE_AGENT_SETTINGS,
+  FakeModelProvider,
+  type FakeModelProviderOptions,
+  type FakeScript,
+  type FakeStep,
+  type FakeToolCall,
+  type FakeToolResult,
+} from "./pi/fake";
+export {
+  checkToolCall,
+  DEFAULT_COMPACTION_INSTRUCTIONS,
+  PiAgentRuntime,
+  type PiAgentRuntimeOptions,
+} from "./pi/runtime";
+export { sessionPathFor } from "./pi/session";
+export { isSensitiveKey, REDACTED, redactForModel, redactString, summarizeForLog } from "./redact";
+export * from "./runtime/port";
+export {
+  type AgentSettings,
+  AgentSettingsSchema,
+  type AgentThinkingLevel,
+  describeSettings,
+  type ResolvedAgentSettings,
+  resolveAgentSettings,
+  THINKING_LEVELS,
+} from "./settings";
+export { buildSystemPrompt, type SystemPromptInput } from "./system-prompt";