feat: migrate to react-markdown for robust markdown rendering

- Replace custom markdown parser with react-markdown + remark-gfm
- Fix document link navigation (./ and ../ references)
- Simplify doc viewing flow (direct markdown content instead of parsed structure)
- Update electron main process to only use api folder for docs
- Add blueprint loading from docs/blueprint.md dynamically
- Fix sidebar file selection path matching
- Update preload scripts for new API structure

.gitignore

@@ -3,3 +3,6 @@ dist/
 .vite/
 *.log
 .DS_Store
+release/
+nul
+skills/