chore: ignore desktop packaging artifacts

Add dist-electron/ and common installer artifact patterns (*.dmg,
*.zip blockmaps, *.AppImage, etc.) to .gitignore so electron-builder
output never gets staged into commits.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -8,8 +8,17 @@ node_modules/
 
 # Build output
 dist/
+dist-electron/
 *.tsbuildinfo
 
+# Desktop packaging artifacts
+*.dmg
+*.dmg.blockmap
+*.zip.blockmap
+*.AppImage
+*.exe
+*.nupkg
+
 # Coverage reports
 coverage/