refactor: extract autoFormat utils from ChatMessage to lib with tests

- Move guessLanguage, looksLikeCode, autoFormatText to src/lib/autoFormat.ts
- Add comprehensive test suite (23 tests) covering language detection, code detection, and auto-formatting
- Reduce ChatMessage.tsx by ~90 lines
- Total tests: 238 (up from 215)

package.json

@@ -1,6 +1,6 @@
 {
   "name": "pinchchat",
-  "version": "1.68.2",
+  "version": "1.68.3",
   "description": "A sleek, dark-themed webchat UI for OpenClaw — monitor sessions, stream responses, and inspect tool calls in real-time.",
   "type": "module",
   "repository": {