refactor: consolidate shared regex patterns and token validation

- Create src/utils/regex-patterns.ts with ANSI_ESCAPE_PATTERN_FULL,
  ANSI_ESCAPE_PATTERN_SIMPLE, TOKEN_PATTERN, and helper functions
- Create src/utils/token-validation.ts with MAX_SESSION_TOKENS and
  validation utilities
- Update session.ts, respawn-controller.ts, ai-checker-base.ts,
  ralph-tracker.ts, state-store.ts to use shared utilities
- Export all new utilities from src/utils/index.ts

Reduces code duplication while maintaining pre-compiled patterns
for performance.

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

src/ai-checker-base.ts

@@ -29,6 +29,7 @@ import { tmpdir } from 'node:os';
 import { join } from 'node:path';
 import { EventEmitter } from 'node:events';
 import { getAugmentedPath } from './session.js';
+import { ANSI_ESCAPE_PATTERN_SIMPLE } from './utils/index.js';
 
 // ========== Types ==========
 
@@ -85,9 +86,6 @@ export interface AiCheckerEvents<R> {
 
 // ========== Constants ==========
 
-/** ANSI escape code pattern for stripping terminal formatting */
-const ANSI_ESCAPE_PATTERN = /\x1b\[[0-9;]*[A-Za-z]/g;
-
 /** Poll interval for checking temp file completion */
 const POLL_INTERVAL_MS = 500;
 
@@ -354,7 +352,7 @@ export abstract class AiCheckerBase<
 
   private async runCheck(terminalBuffer: string): Promise<R> {
     // Prepare the terminal buffer (strip ANSI, trim to maxContextChars)
-    const stripped = terminalBuffer.replace(ANSI_ESCAPE_PATTERN, '');
+    const stripped = terminalBuffer.replace(ANSI_ESCAPE_PATTERN_SIMPLE, '');
     const trimmed = stripped.length > this.config.maxContextChars
       ? stripped.slice(-this.config.maxContextChars)
       : stripped;