fix: make AI chat work on free Vercel plans - #476

Summary

Deploying YCode on a Vercel hobby (free) plan failed because the AI chat route exported maxDuration = 800, which exceeds the hobby-plan limit of 300 seconds and fails build validation. The route-level export also always overrode vercel.json, so paid deployments couldn't configure their own limit either.

Changes

• Remove the maxDuration = 800 export from the AI chat route and set it in vercel.json instead (300s — the hobby-plan maximum), so deployments can override it in their own vercel.json
• Derive the agent loop's run budget (MAX_RUN_MS) from a new optional AI_CHAT_MAX_DURATION env var (defaults to 300s, minus a 60s buffer), so the agent still stops gracefully before Vercel hard-kills the function
• Document AI_CHAT_MAX_DURATION in .env.example, including the requirement to keep it in sync with vercel.json on paid plans

Test plan

• Deploy to a Vercel hobby plan — build validation should pass
• Run a long AI chat session and confirm it ends gracefully with a resumable "ran out of time" error instead of a silent cut
• On a paid deployment, raise maxDuration in vercel.json and set AI_CHAT_MAX_DURATION to match — confirm longer runs are allowed

Made with Cursor