fix: set default AGENT_BASE_URL to production doc-agents URL

[devin-ai-integration]

Summary

Fixes 503 errors on AI search by setting a default value for AGENT_BASE_URL to https://p0f83a312791b60ff.agentuity.run. Previously, the middleware returned 503 if this env var was not explicitly set.

Changes:

• Added default AGENT_BASE_URL in lib/config.ts and middleware.ts
• Simplified middleware error handling to only check for AGENT_BEARER_TOKEN (since AGENT_BASE_URL now has a default)

Review & Testing Checklist for Human

• Verify the hardcoded URL is correct: Confirm https://p0f83a312791b60ff.agentuity.run is the intended production doc-agents endpoint
• Test AI search after deployment: Open the docs site, click the sparkles icon, and submit a query to verify the 503 error is resolved
• Verify AGENT_BEARER_TOKEN is set in Cloudflare: This env var is still required and will cause 503 if missing

Note: The default URL is duplicated in two files. Consider extracting to a shared constant if this becomes a maintenance concern.

Notes

• Link to Devin run: https://app.devin.ai/sessions/a407919e735448c8aac02b7ba0a123f4
• Requested by: @afterrburn

Summary by CodeRabbit

• Chores
  • Enhanced configuration defaults for backend connectivity, reducing setup requirements.
  • Improved error messaging for environment variable validation.

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[devin-ai-integration]

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📝 Walkthrough

Walkthrough

This PR introduces a default backend URL configuration constant and updates the agent base URL initialization logic to fall back to this default when environment variables are not provided. The explicit AGENT_BASE_URL requirement check has been removed with simplified error handling.

Changes

Cohort / File(s)	Summary
Agent Base URL Configuration lib/config.ts, middleware.ts	Introduced DEFAULT_AGENT_BASE_URL constant; agentBaseUrl now falls back to this default when environment variable not set; removed AGENT_BASE_URL requirement check in middleware; simplified error handling to only require AGENT_BEARER_TOKEN for authenticated endpoints

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📥 Commits

Reviewing files that changed from the base of the PR and between 217f3d3 and 4f851f1.

📒 Files selected for processing (2)

• lib/config.ts
• middleware.ts

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