feat: implement proper orchestrator workflow with reconciliation loop

Rewrite OrchestratorWorkflow as true reconciliation loop:
- PlanningActivity decides what tasks to dispatch
- Fan-out TaskUnit workflows for parallel execution
- Each TaskUnit runs Implementer → Test → Judge → Commit
- Judge reviews code quality, retries on failure with lessons
- Fan-in waits for all TaskUnits
- Board update and squash merge on success
- continue-as-new for long-running workflows
- Proper error handling and signal support

Key changes:
- statemachine/orchestrator.go: Reconciliation loop (Plan → Dispatch → Review → Repeat)
- statemachine/taskunit.go: Task execution with retry loop & judge review
- statemachine/types.go: Updated TaskUnitInput/Output for new workflow
- cmd/worker/main.go: Register RunIntegrationTestActivity
- action/integration.go: Renamed from integration_test.go (fix Go build issue)

Models:
- Planner: reasoning (OpenAI-compatible from local LLM API)
- Judge: reasoning (reviews diff + tests, gates success)
- Implementer: ornith:35b (executes tasks)

Verification: go build ./cmd/worker ./cmd/starter ✓

cmd/worker/main.go

@@ -64,7 +64,7 @@ func main() {
 	w.RegisterActivity(action.ImplementerActivity)
 	w.RegisterActivity(action.JudgeActivity)
 	// Integration and lessons activities - register when fully tested
-	// w.RegisterActivity(action.RunIntegrationTestActivity)
+	w.RegisterActivity(action.RunIntegrationTestActivity)
 	// w.RegisterActivity(action.UpdateLessonsActivity)
 	// w.RegisterActivity(action.ReadLessonsActivity)