feat: add model selection for AI agents (claude, codex, gemini)

Add a new ModelSelector component that allows users to choose specific model variants for different AI agents. This includes:
- ModelSelector UI component with agent-specific model options
- Model parameter propagation through API, RPC, and spawning layers
- Support for auto model selection (default behavior)
- Localization strings for English and Chinese
- Type definitions for model options per agent

cli/src/runner/run.ts

@@ -333,6 +333,9 @@ export async function startRunner(): Promise<void> {
           '--hapi-starting-mode', 'remote',
           '--started-by', 'runner'
         ];
+        if (options.model) {
+          args.push('--model', options.model);
+        }
         if (yolo) {
           args.push('--yolo');
         }