feat(opencode): Phase 7 - Frontend TypeScript type definitions

- Add "opencode" to AppId type in lib/api/types.ts
- Extend McpApps interface with opencode field in types.ts
- Add OpenCode-specific types: OpenCodeModel, OpenCodeProviderOptions,
  OpenCodeProviderConfig, OpenCodeMcpServerSpec
- Add opencodeConfigDir to Settings interface
- Add importOpenCodeFromLive() to providersApi
- Fix type errors across components:
  - AppSwitcher: add opencode to icon/name mappings
  - McpFormModal: add opencode to enabledApps state
  - PromptFormModal/Panel: add opencode filename mapping
  - EndpointSpeedTest: add opencode timeout config
  - useBaseUrlState: add opencode to appType union
  - ProxyToggle: add opencode label
  - App.tsx: handle opencode fallback for SkillsPage
- Update ProxyTakeoverStatus with opencode field (always false)
- Fix test mocks in tests/msw/state.ts

src/App.tsx

@@ -454,7 +454,7 @@ function App() {
             />
           );
         case "skillsDiscovery":
-          return <SkillsPage ref={skillsPageRef} initialApp={activeApp} />;
+          return <SkillsPage ref={skillsPageRef} initialApp={activeApp === "opencode" ? "claude" : activeApp} />;
         case "mcp":
           return (
             <UnifiedMcpPanel