fix(P01): add SIGTERM/SIGINT signal handlers for graceful shutdown

---ci---
project: ci
phase: 1
milestone: v0.8
status: in_progress
decisions:
  - id: D-026
    decision: Graceful drain on SIGTERM/SIGINT: dispose timers then exit
    rationale: Prevents orphaned setTimeout timers from leaking when process is killed
    confidence: 0.88
requirements:
  covered: [FIX-07]
---/ci---

FIX-07: cli/index.ts registers SIGTERM/SIGINT handlers that call
escalationProtocol.dispose() before process.exit. OrchestratorAgent
registers its EscalationProtocol instance via registerEscalationProtocol().
SIGINT exits with code 130, SIGTERM with 143 (standard signal+128 convention).

src/agents/orchestrator.ts

@@ -19,6 +19,7 @@ import { Specification, parseSpecification } from "../types/specification.js";
 import { loadConfig, saveConfig, isCIAgentInitialized, initCIAgent } from "../core/config.js";
 import { getAgent } from "./index.js";
 import { IntelligenceBackend, BackendUnavailableError } from "../backends/types.js";
+import { registerEscalationProtocol } from "../cli/index.js";
 import { execSync } from "node:child_process";
 
 export interface GitAgentContext extends AgentContext {
@@ -87,6 +88,7 @@ export class OrchestratorAgent extends BaseAgent {
 
       this.decisionEngine = new DecisionEngine(this.config, context.project_path, this.currentMilestone);
       this.escalationProtocol = new EscalationProtocol(this.config, context.project_path, this.currentMilestone);
+      registerEscalationProtocol(this.escalationProtocol);
 
       while (this.pipelineState.current_phase <= this.totalPhases) {
         this.log(`Processing phase ${this.pipelineState.current_phase} of ${this.totalPhases}`);