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/web/server.ts

@@ -120,6 +120,7 @@ import {
   ITERATION_PAUSE_MS,
   BATCH_FLUSH_THRESHOLD,
   STATS_COLLECTION_INTERVAL_MS,
+  INACTIVITY_TIMEOUT_MS,
 } from '../config/server-timing.js';
 
 // DEC mode 2026 - Synchronized Output
@@ -230,7 +231,7 @@ export class WebServer extends EventEmitter {
   // Adaptive batching: track rapid events to extend batch window (per-session)
   // StaleExpirationMap auto-cleans entries for sessions that stop generating output
   private lastTerminalEventTime: StaleExpirationMap<string, number> = new StaleExpirationMap({
-    ttlMs: 5 * 60 * 1000, // 5 minutes - auto-expire stale session timing data
+    ttlMs: INACTIVITY_TIMEOUT_MS, // 5 minutes - auto-expire stale session timing data
     refreshOnGet: false, // Don't refresh on reads, only on explicit sets
   });
   // Centralized cleanup for standalone timers (intervals + resettable timeouts)
@@ -2397,7 +2398,7 @@ export class WebServer extends EventEmitter {
       () => {
         this.recordPeriodicTokenUsage();
       },
-      5 * 60 * 1000,
+      INACTIVITY_TIMEOUT_MS,
       { description: 'periodic token recording' }
     );