[Agent] Search shows changelog results when feed disabled

Agent brief

Category: bug | Severity: medium | Effort: S

Problem

Search API returns changelog hits even when project.changelog_enabled is false. Users click a result and land on a 404 Updates page.

Repro

1. Disable changelog in project settings
2. Open command palette, search for a known changelog title
3. Result appears; click → 404

Files

• src/app/api/search/route.ts — filter changelog query on changelog_enabled

Acceptance criteria

• No changelog results when feed disabled
• Docs/posts still searchable
• Add test in route test file if exists

Suggested approach

Join projects table or filter in post-processing; mirror leaderboard gating pattern.