fix: theme loading when installed via mise (fixes #681)

mise flattens tarball structure, placing theme files at root instead of theme/.
Fall back to root directory if theme/ subdirectory doesn't exist.

packages/coding-agent/src/config.ts

@@ -52,7 +52,13 @@ export function getPackageDir(): string {
  */
 export function getThemesDir(): string {
 	if (isBunBinary) {
-		return join(dirname(process.execPath), "theme");
+		const execDir = dirname(process.execPath);
+		const themeDir = join(execDir, "theme");
+		// Fall back to root if theme/ doesn't exist (mise flattens directory structure)
+		if (existsSync(themeDir)) {
+			return themeDir;
+		}
+		return execDir;
 	}
 	// Theme is in modes/interactive/theme/ relative to src/ or dist/
 	const packageDir = getPackageDir();