feat(cli-settings): support multi-provider settings for Claude, Codex, and Gemini

Decouple CLI settings architecture from Claude-only to support multiple
providers. Each provider has independent settings UI and backend handling.

- Add CliProvider type discriminator ('claude' | 'codex' | 'gemini')
- Add CodexCliSettings (profile, authJson, configToml) and GeminiCliSettings types
- Update EndpointSettings with provider field (defaults 'claude' for backward compat)
- Refactor CliSettingsModal with provider selector and provider-specific forms
- Remove includeCoAuthoredBy field across all layers
- Extend CliConfigModal to show Config Profile for all tools (not just claude)
- Add provider-aware argument injection in cli-session-manager (--settings/--profile/env)
- Rename addClaudeCustomEndpoint to addCustomEndpoint (old name kept as deprecated alias)
- Replace providerBasedCount/directCount with per-provider counts in useCliSettings hook
- Update CliSettingsList with provider badges and per-provider stat cards
- Add Codex and Gemini test cases for validateSettings and createDefaultSettings

ccw/src/core/routes/cli-settings-routes.ts

@@ -56,8 +56,8 @@ export async function handleCliSettingsRoutes(ctx: RouteContext): Promise<boolea
         if (!request.settings || !request.settings.env) {
           return { error: 'settings.env is required', status: 400 };
         }
-        // Deep validation of settings object
-        if (!validateSettings(request.settings)) {
+        // Deep validation of settings object (provider-aware)
+        if (!validateSettings(request.settings, request.provider)) {
           return { error: 'Invalid settings object format', status: 400 };
         }