feat: comprehensive codebase improvements (cleanup, logic, performance)

Code Cleanups:
- Consolidated PlanTaskStatus and TddPhase types to types.ts
- Standardized node: prefix for Node.js builtin imports
- Fixed timer type to NodeJS.Timeout in respawn-controller

Logic Improvements:
- Fixed AI check race condition with UUID tracking in respawn-controller
- Added comprehensive _isStopped guards in session timer callbacks
- Made RalphTracker reset events non-reentrant via process.nextTick()
- Improved SessionManager mutex pattern reliability

Performance Optimizations:
- Fixed pendingToolCalls memory leak with TTL cleanup in subagent-watcher
- Improved LRUMap.newest() from O(n) to O(1) with _newestKey tracking

Documentation:
- Enhanced README antiflicker section with 6-layer technical details

Version: 0.1441

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/types.ts

@@ -93,6 +93,12 @@ export type TaskStatus = 'pending' | 'running' | 'completed' | 'failed';
 /** Status of the Ralph Loop controller */
 export type RalphLoopStatus = 'stopped' | 'running' | 'paused';
 
+/** Task execution status for plan tracking */
+export type PlanTaskStatus = 'pending' | 'in_progress' | 'completed' | 'failed' | 'blocked';
+
+/** TDD phase categories */
+export type TddPhase = 'setup' | 'test' | 'impl' | 'verify' | 'review';
+
 // ========== Session Types ==========
 
 /**