feat: Implement slash command functionality in the orchestrator

- Refactored NodePalette to remove unused templates and streamline the UI.
- Enhanced PropertyPanel to support slash commands with input fields for command name and arguments.
- Introduced TagEditor for inline variable editing and custom template creation.
- Updated PromptTemplateNode to display slash command badges and instructions.
- Modified flow types to include slashCommand and slashArgs for structured execution.
- Adjusted flow executor to construct instructions based on slash command fields.

ccw/frontend/src/lib/api.ts

@@ -1089,6 +1089,8 @@ export interface Command {
   location?: 'project' | 'user';
   path?: string;
   relativePath?: string;
+  argumentHint?: string;
+  allowedTools?: string[];
 }
 
 export interface CommandsResponse {