feat: add Codex CLI provider with local login (WIP)

[roomote]

Description

This PR attempts to address Issue #8049 by adding a new Codex CLI provider that works like OpenAI but uses local login instead of API keys.

Current Implementation

✅ Added 'codex-cli' to provider types and schemas
✅ Created CodexCliHandler that extends OpenAI behavior with local auth
✅ Created UI component with sign in/out functionality
✅ Added support for the same models as OpenAI
✅ No API key management required - uses local session tokens

Status: Work in Progress

This implementation currently uses placeholder/mock authentication to demonstrate the UI flow. As noted in the issue comments, I need clarification on:

1. The actual CLI tool details (name, authentication flow, token format)
2. Whether to integrate with ChatMock directly or create a similar implementation
3. Specific authentication flow requirements (browser-based OAuth, device code, etc.)
4. Message handler implementation details

Related Issue

Closes #8049 (pending completion of actual CLI integration)

Testing

The basic structure compiles and passes type checks. Full testing will be added once the authentication implementation is finalized.

Next Steps

Awaiting feedback on the implementation questions posted in the issue before completing the actual CLI integration.

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Note: This is a work-in-progress PR to share the current implementation structure. The authentication functionality uses mock implementations pending clarification of requirements.

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Important

Introduces Codex CLI provider for local authentication, mimicking OpenAI, with UI and model support, but currently uses mock authentication.

• Behavior:
  • Adds CodexCliHandler in src/api/providers/codex-cli.ts for local CLI authentication, mimicking OpenAI behavior.
  • Supports same models as OpenAI, defined in codex-cli.ts.
  • UI component CodexCli in CodexCli.tsx for sign in/out functionality.
• Schemas and Models:
  • Adds codexCliSchema to provider-settings.ts for provider settings.
  • Defines codexCliModels in codex-cli.ts with model details.
• Integration:
  • Registers CodexCliHandler in index.ts and providers/index.ts.
  • Updates useSelectedModel.ts to handle Codex CLI models.
• Misc:
  • Adds codex-cli to providerNames in provider-settings.ts.
  • Mock authentication flow in CodexCli.tsx for UI demonstration.

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[roomote]

I wrote this code blindfolded and it shows.

Critical Issues Found

1. Missing UI Integration - The CodexCli component is not wired up in ApiOptions.tsx. Need to add a case for 'codex-cli' provider.

2. Missing constants.ts Entry - codexCliModels not added to MODELS_BY_PROVIDER and 'codex-cli' not in PROVIDERS array.

3. Incomplete Message Handlers - No webview message handlers for codexCliSignIn, codexCliSignOut, and codexCliDetect in webviewMessageHandler.ts.

4. Mock Implementation - Using placeholder authentication with setTimeout instead of actual CLI integration.

5. Hardcoded OpenAI URL - Line 61 in codex-cli.ts hardcodes https://api.openai.com/v1 which won't work for local CLI.

6. No Tests - Missing test coverage for the new provider.

7. Security Concern - Session tokens should use VS Code's secret storage.

8. Unused Imports - Several unused imports in codex-cli.ts (Anthropic, vscode, path, fs).

9. UI Issues - Incorrect checkbox class in CodexCli.tsx line 151.

This is marked as WIP which explains the mock implementation, but the missing integration points need to be addressed before this can be merged.