feat: add Codex CLI detection and model management APIs

- Implemented IPC handlers for checking Codex CLI installation status, retrieving available models, and checking provider statuses.
- Enhanced the SettingsView to include OpenAI API key management and connection testing.
- Updated the feature executor to support multiple model providers (Claude and Codex), allowing for improved flexibility in feature execution.
- Introduced utility functions to determine model types and support for thinking controls.

This update enhances the application's capabilities by integrating Codex CLI support and improving model management, providing users with a more robust experience.

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

app/electron/preload.js

@@ -141,6 +141,22 @@ contextBridge.exposeInMainWorld("electronAPI", {
 
   // Claude CLI Detection API
   checkClaudeCli: () => ipcRenderer.invoke("claude:check-cli"),
+
+  // Codex CLI Detection API
+  checkCodexCli: () => ipcRenderer.invoke("codex:check-cli"),
+
+  // Model Management APIs
+  model: {
+    // Get all available models from all providers
+    getAvailable: () => ipcRenderer.invoke("model:get-available"),
+
+    // Check all provider installation status
+    checkProviders: () => ipcRenderer.invoke("model:check-providers"),
+  },
+
+  // OpenAI API
+  testOpenAIConnection: (apiKey) =>
+    ipcRenderer.invoke("openai:test-connection", { apiKey }),
 });
 
 // Also expose a flag to detect if we're in Electron