feat(KB-004): add GitHub PR creation and comment monitoring

- Add PR fields (prInfo, prNumber, prUrl) to Task type and TaskStore with updatePrInfo method
- Add PR Management API endpoints: create, status, refresh with per-repo rate limiting
- Add GitHubClient for PR creation and status fetching with comment support
- Add PrSection component for PR status display and actions in dashboard
- Add PR comment monitoring engine with PrMonitor and PrCommentHandler
- Integrate PR monitoring into scheduler for automatic PR tracking
- Add comprehensive tests for PR features in all packages

packages/engine/src/index.ts

@@ -9,3 +9,5 @@ export { createKbAgent, type AgentOptions, type AgentResult } from "./pi.js";
 export { WorktreePool, scanIdleWorktrees, cleanupOrphanedWorktrees } from "./worktree-pool.js";
 export { createLogger, type Logger } from "./logger.js";
 export { isUsageLimitError, UsageLimitPauser } from "./usage-limit-detector.js";
+export { PrMonitor, type PrComment, type TrackedPr, type OnNewCommentsCallback } from "./pr-monitor.js";
+export { PrCommentHandler } from "./pr-comment-handler.js";