fix(ci): resolve release pipeline conflicts and clean repo structure

- Delete conflicting .releaserc.json (keep release.config.cjs as single source)
- Fix repo URL from Draculabo/AntigravityManager to evandrodevbr/GeminiNexus
- Fix @semantic-release/git to commit pnpm-lock.yaml (not package-lock.json)
- Normalize Node.js version to 20 across all workflows
- Add packageManager field to package.json for pnpm consistency
- Update AGENTS.md: npm -> pnpm (18 references)
- Update .gitignore: add tools/, thoughts/, binaries, one-shot scripts

package.json

@@ -5,6 +5,7 @@
   "description": "Gemini Nexus - Electron App",
   "main": ".vite/build/main.js",
   "private": true,
+  "packageManager": "[email protected]",
   "scripts": {
     "start": "cross-env DEBUG=electron-forge:* electron-forge start",
     "dev": "cross-env DEBUG=electron-forge:* electron-forge start",