feat(workflow): add thread/edge location support (#558)

Implement thread-level and edge-level working directory management:

- Thread-level cwd (required, defaults to process.cwd())
  - Captured at uwf thread start time
  - Stored in StartNodePayload
  - Inherited by all steps unless overridden

- Edge-level location (optional, supports mustache templates)
  - New location: string | null field on Target type
  - Resolved by moderator using previous step's output
  - Example: location: "{{{repoPath}}}"

- Step audit trail
  - Each StepNodePayload records actual cwd where agent executed

Changes:
- workflow-protocol: Add cwd to StartNodePayload & StepRecord, location to Target
- cli-workflow: Thread start captures cwd, moderator resolves location, step execution uses resolved cwd
- workflow-util-agent: Expose cwd in agent context

Tests:
- Protocol type tests (3 scenarios)
- Moderator location resolution tests (5 scenarios)
- Thread-location integration tests (3 scenarios)

All tests pass. Build successful. Backward compatible.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/workflow-util-agent/src/context.ts

@@ -130,6 +130,7 @@ async function buildHistory(
       edgePrompt: step.edgePrompt ?? "",
       startedAtMs: step.startedAtMs,
       completedAtMs: step.completedAtMs,
+      cwd: step.cwd ?? "",
       content,
     });
   }

packages/workflow-util-agent/src/run.ts

@@ -72,6 +72,7 @@ async function writeStepNode(options: {
     edgePrompt: options.edgePrompt,
     startedAtMs: options.startedAtMs,
     completedAtMs: options.completedAtMs,
+    cwd: process.cwd(),
   };
   const hash = await options.store.put(options.schemas.stepNode, payload);
   const node = options.store.get(hash);