feat: tool timeout auto-retry, file tree attachment, force stop button

- Add configurable tool timeout with auto-retry: when a tool exceeds the
  timeout threshold, abort and send a follow-up message asking Claude to
  try a different approach
- Add "+" button on file tree items to attach files directly to chat
  input via new /api/files/raw endpoint and custom event bridge
- Add force stop button in streaming status bar when tool runs >90s,
  with warning indicators at 60s
- Improve doc preview markdown rendering (padding, list indentation)
- Bump version to 0.10.0

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

package.json

@@ -1,6 +1,6 @@
 {
   "name": "codepilot",
-  "version": "0.9.0",
+  "version": "0.10.0",
   "private": true,
   "author": {
     "name": "op7418",