feat: add Orchestrator Loop — phased plan execution with team agents

Adds a new autonomous loop that accepts high-level goals, generates
phased execution plans via AI, and executes them step-by-step with
verification gates between phases.

Core components:
- OrchestratorLoop: state machine (idle→planning→approval→executing→verifying→completed)
- OrchestratorPlanner: plan generation via PlanOrchestrator, Kahn's algorithm phase grouping
- OrchestratorVerifier: phase verification (strict/moderate/lenient modes)
- Prompt templates for phase execution, team delegation, verification, replanning

API (10 endpoints):
- POST start/approve/reject/pause/resume/stop
- GET status/plan
- POST phase/:id/skip, phase/:id/retry

Frontend: orchestrator-panel.js with SSE-driven state, phase progress, task tracking

Tests: 22 tests (18 route + 4 unit), all passing. Typecheck/lint/format clean.

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

src/prompts/index.ts

@@ -7,3 +7,10 @@
 
 export { RESEARCH_AGENT_PROMPT } from './research-agent.js';
 export { PLANNER_PROMPT } from './planner.js';
+export {
+  PHASE_EXECUTION_PROMPT,
+  TEAM_LEAD_PROMPT,
+  VERIFICATION_PROMPT,
+  REPLAN_PROMPT,
+  SINGLE_TASK_PROMPT,
+} from './orchestrator.js';