docs: add comprehensive JSDoc for installPlugins function

Added detailed JSDoc documentation including:
- Full function description with behavior details
- Parameter documentation with examples
- Return value description
- Throws documentation for all error cases
- Usage examples showing common scenarios

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: whyuan-cc

base-action/src/install-plugins.ts

@@ -66,7 +66,40 @@ async function installPlugin(
 }
 
 /**
- * Installs Claude Code plugins from a comma-separated list
+ * Installs Claude Code plugins from a comma-separated list.
+ *
+ * Parses the plugin list, validates each plugin name for security (checking for
+ * command injection attempts and invalid characters), and sequentially installs
+ * each plugin using the `claude plugin install` command. Installation stops on
+ * the first error encountered.
+ *
+ * @param pluginsInput - Comma-separated list of plugin names to install (e.g., "plugin1,plugin2,plugin3").
+ *                       Can include whitespace which will be trimmed. Empty entries are ignored.
+ *                       If undefined, empty, or whitespace-only, no plugins are installed.
+ * @param claudeExecutable - Path to the Claude Code executable. Defaults to "claude".
+ *                           Use a custom path if Claude Code is installed in a non-standard location.
+ *
+ * @returns A promise that resolves when all plugins are successfully installed.
+ *
+ * @throws {Error} If a plugin name contains invalid characters (must match `/^[@a-zA-Z0-9_\-\/\.]+$/`)
+ * @throws {Error} If a plugin name exceeds 256 characters
+ * @throws {Error} If plugin installation fails (non-zero exit code or spawn error)
+ *
+ * @example
+ * ```typescript
+ * // Install multiple plugins with default executable
+ * await installPlugins("plugin1,plugin2,plugin3");
+ *
+ * // Install plugins with custom Claude Code path
+ * await installPlugins("@scope/plugin,org/plugin-name", "/usr/local/bin/claude");
+ *
+ * // Handle errors
+ * try {
+ *   await installPlugins("plugin1,plugin2");
+ * } catch (error) {
+ *   console.error("Plugin installation failed:", error);
+ * }
+ * ```
  */
 export async function installPlugins(
   pluginsInput: string | undefined,