feat: add default modes for profile dropdown in provider settings

[roomote-v0]

This PR attempts to address Issue #12227. Feedback and guidance are welcome.

Summary

Adds a "Default for modes" multi-select dropdown in the provider settings section. Users can now see and configure which modes should use a specific provider profile as their default. When switching to a selected mode, the assigned profile will be activated automatically.

Changes

Backend

• packages/types/src/vscode-extension-host.ts: Added setDefaultModesForProfile message type to WebviewMessage
• src/core/config/ProviderSettingsManager.ts: Added unsetModeConfig() and getAllModeConfigs() methods
• src/core/webview/webviewMessageHandler.ts: Added handler for the new message that assigns/unassigns modes to profiles and syncs modeApiConfigs to global state

Frontend

• webview-ui/src/components/settings/ApiConfigManager.tsx: Added a dropdown using DropdownMenuCheckboxItem that shows all available modes. Checked modes indicate that the current profile is the default for that mode.
• webview-ui/src/components/settings/SettingsView.tsx: Pass modeApiConfigs and customModes to ApiConfigManager
• webview-ui/src/i18n/locales/en/settings.json: Added translation strings

Tests

• Added tests for unsetModeConfig and getAllModeConfigs in ProviderSettingsManager.spec.ts (4 new tests, all passing)
• Updated ApiConfigManager.spec.tsx mocks to include DropdownMenu components (13 tests, all passing)

How it works

1. Each provider profile shows a "Default for modes" dropdown listing all available modes (built-in + custom)
2. Checking a mode assigns the current profile as the default for that mode
3. Unchecking a mode removes the assignment (falls back to whatever profile the mode had before)
4. If a custom mode is deleted, it simply disappears from the dropdown (no stale entries shown)
5. Changes are persisted immediately via ProviderSettingsManager and synced to the webview

Interactively review PR in Roo Code Cloud