feat: IME-aware chat input, message copy button, Git path scanning

- Fix IME composition issue: Enter during Chinese/Japanese/Korean input
  method composition no longer prematurely sends messages (assistant.js)
  Uses e.isComposing + keyCode 229 guard on keydown handler
- Add one-click copy button to chat message bubbles (both chat.js and
  assistant.js), with hover-reveal animation and checkmark feedback
- Add 'copy' icon to SVG icon library (Lucide style)
- Add CSS for msg-copy-btn in chat.css and assistant.css
- Implement scan_git_paths Rust command: scans common Git installation
  locations on Windows/macOS/Linux (Program Files, Scoop, Chocolatey,
  GitHub Desktop, VS Code, MSYS2, Homebrew, Xcode CLT, etc.)
- Register scan_git_paths in lib.rs, tauri-api.js, dev-api.js
- Add scan button + results UI in settings.js Git path section
- Add i18n keys: gitScan, gitScanning, gitScanEmpty, gitScanUse

src/lib/icons.js

@@ -22,6 +22,7 @@ const PATHS = {
   'bar-chart': '<line x1="12" y1="20" x2="12" y2="10"/><line x1="18" y1="20" x2="18" y2="4"/><line x1="6" y1="20" x2="6" y2="16"/>',
   'home': '<path d="M3 9l9-7 9 7v11a2 2 0 01-2 2H5a2 2 0 01-2-2z"/><polyline points="9 22 9 12 15 12 15 22"/>',
   'paperclip': '<path d="M21.44 11.05l-9.19 9.19a6 6 0 01-8.49-8.49l9.19-9.19a4 4 0 015.66 5.66l-9.2 9.19a2 2 0 01-2.83-2.83l8.49-8.48"/>',
+  'copy': '<rect x="9" y="9" width="13" height="13" rx="2" ry="2"/><path d="M5 15H4a2 2 0 01-2-2V4a2 2 0 012-2h9a2 2 0 012 2v1"/>',
   'clipboard': '<path d="M16 4h2a2 2 0 012 2v14a2 2 0 01-2 2H6a2 2 0 01-2-2V6a2 2 0 012-2h2"/><rect x="8" y="2" width="8" height="4" rx="1" ry="1"/>',
   'file': '<path d="M13 2H6a2 2 0 00-2 2v16a2 2 0 002 2h12a2 2 0 002-2V9z"/><polyline points="13 2 13 9 20 9"/>',
   'file-text': '<path d="M14 2H6a2 2 0 00-2 2v16a2 2 0 002 2h12a2 2 0 002-2V8z"/><polyline points="14 2 14 8 20 8"/><line x1="16" y1="13" x2="8" y2="13"/><line x1="16" y1="17" x2="8" y2="17"/><polyline points="10 9 9 9 8 9"/>',

src/lib/tauri-api.js

@@ -287,6 +287,7 @@ export const api = {
   saveCustomNodePath: (nodeDir) => invoke('save_custom_node_path', { nodeDir }).then(r => { invalidate('check_node', 'get_services_status'); invoke('invalidate_path_cache').catch(() => {}); return r }),
   invalidatePathCache: () => invoke('invalidate_path_cache'),
   checkGit: () => cachedInvoke('check_git', {}, 60000),
+  scanGitPaths: () => invoke('scan_git_paths'),
   autoInstallGit: () => invoke('auto_install_git'),
   configureGitHttps: () => invoke('configure_git_https'),
   getDeployConfig: () => cachedInvoke('get_deploy_config'),