feat: implement file editing capabilities with CodeMirror integration

- Added CodeMirror editor for file content editing in FilesView.
- Introduced draft saving functionality with unsaved changes confirmation dialog.
- Implemented file writing API to persist changes to the filesystem.
- Enhanced language support for syntax highlighting based on file extensions.
- Updated UI components to support new editing features, including save and discard options.
- Refactored line selection logic for improved user experience on both desktop and mobile.
- Added new utility functions for language detection by file extension.
- Introduced a new theme for CodeMirror to align with the application's design.

packages/web/src/api/files.ts

@@ -138,4 +138,24 @@ export const createWebFilesAPI = (): FilesAPI => ({
     const content = await response.text();
     return { content, path: target };
   },
+
+  async writeFile(path: string, content: string): Promise<{ success: boolean; path: string }> {
+    const target = normalizePath(path);
+    const response = await fetch('/api/fs/write', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify({ path: target, content }),
+    });
+
+    if (!response.ok) {
+      const error = await response.json().catch(() => ({ error: response.statusText }));
+      throw new Error((error as { error?: string }).error || 'Failed to write file');
+    }
+
+    const result = await response.json().catch(() => ({}));
+    return {
+      success: Boolean((result as { success?: boolean }).success),
+      path: typeof (result as { path?: string }).path === 'string' ? normalizePath((result as { path: string }).path) : target,
+    };
+  },
 });