refactor: codebase cleanup — dead code, regex helper, centralized constants, tests

- Remove unused validateTokenCounts/validateTokensAndCost exports and PlanPhase type alias
- Add execPattern() helper to eliminate 8 repetitive .lastIndex=0 + exec() loops
- Centralize 11 magic number constants into config/ai-defaults.ts and config/server-timing.ts
- Remove stale src/tui from tsconfig.json exclude
- Fix CLAUDE.md inaccuracies (session helpers, app.js line count, module count)
- Add 316 new tests: LRUMap (38), StaleExpirationMap (42), BufferAccumulator (33),
  respawn helpers (142), system-routes expansion (11→61)

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

src/ralph-stall-detector.ts

@@ -10,6 +10,7 @@
  */
 
 import { EventEmitter } from 'node:events';
+import { CLEANUP_CHECK_INTERVAL_MS } from './config/server-timing.js';
 
 /**
  * RalphStallDetector - Detects iteration stalls in the Ralph loop.
@@ -57,7 +58,7 @@ export class RalphStallDetector extends EventEmitter {
     // Check every minute
     this._iterationStallTimer = setInterval(() => {
       this.checkIterationStall();
-    }, 60 * 1000);
+    }, CLEANUP_CHECK_INTERVAL_MS);
   }
 
   /**