feat: integrate OpenAI Codex mode for reasoning tasks

[Anurag13075]

OpenAI Codex Integration 🤖✨
Description
This PR introduces an end-to-end integration of the OpenAI Codex (codex-mini-latest) reasoning model into Bolt.new. The Codex model provides a completely different paradigm for AI coding—rather than a conversational streaming loop, it uses the OpenAI Responses API to deeply reason through complex software tasks and generate structured, comprehensive file tree mutations.

This feature is built as a non-destructive, additive layer that operates seamlessly alongside the existing conversational flow.

Key Features & Changes
🔑 Settings Panel / API Key Config: Added a new robust Settings overlay (accessible via the sidebar menu) to safely store and manage the OPENAI_API_KEY. It persists to a cookie to seamlessly pipe into the server action, or falls back to Cloudflare env bindings.
🎛️ Codex Toggle Switch: Added a "Codex / Instant" badge toggle directly into the chat toolbar. It enables users to explicitly opt into deep reasoning mode.
⏳ Live Execution Tracker: Implemented a responsive CodexProgress UI widget that gives users live feedback on the reasoning process (e.g., "Planning file changes...", "Writing implementation..."), along with an elapsed timer to mitigate UX friction during longer reasoning loops (30-120s).
⚙️ Remix API Action (api.codex.ts): Built a robust backend passthrough for the OpenAI Responses API that validates the API Key, safely compiles the current file tree context from the WebContainer, sets the 16k output tokens max, and feeds the resulting string straight back into the client pipeline.
⚡ Zero-Regression Architecture: Integrated directly into workbenchStore and the existing StreamingMessageParser. This ensures that Codex's structured files trace exactly the same execution path as normal chat without interfering with the standard streaming infrastructure.
🔧 Bug Fixes: Lazily loaded the workbenchStore inside BaseChat.tsx to fix a path-browserify SSR reference error that leaked into the Vite node environment.
Visuals
(Feel free to add screenshots or screen recordings of the feature here!)

Testing Checklist
Configured OPENAI_API_KEY in worker-configuration.d.ts and wrangler.toml
Verified Settings UI successfully saves the API Key to local cookies.
Tested the Codex toggle UX and chat placeholder updates.
Submitted a prompt in Codex mode, verifying the CodexProgress state rotates and handles elapsed time properly.
Verified the api.codex.ts endpoint successfully fetches and parses the response.
Verified the generated code executes and updates the WebContainer accurately.
Ensured standard Instant mode operates without interference or regressions.
Notes
The codex-mini-latest endpoint relies on the v1/responses API format and requires native fetch capabilities to maintain package leanness. No heavy SDKs were installed.

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