Background task fails: 'Unexpected response status 200' when checking GitHub app installation

Bug Description

Background/remote tasks fail with:

Cannot launch remote Claude Code session.

The Claude GitHub app must be installed on this repository first.

The GitHub app IS installed with access to all repositories.

Root Cause (from debug log)

[DEBUG] Checking GitHub app installation for j9o/relentless-execution
[DEBUG] checkGithubAppInstalled: Unexpected response status 200

The CLI receives HTTP 200 (success) but treats it as "unexpected" and fails.

Environment

• Claude Code: 2.0.76 (latest)
• Platform: macOS Darwin 25.1.0
• Repository: Private repo on GitHub

Verified Setup

• ✅ Claude GitHub app installed (Settings → Applications → Installed GitHub Apps)
• ✅ App has "All repositories" access
• ✅ Admin permissions on repo
• ✅ .github/workflows/claude.yml exists
• ✅ ANTHROPIC_API_KEY secret set
• ✅ gh auth status valid with repo/workflow scopes
• ✅ git rev-parse --is-inside-work-tree returns true
• ✅ Tested with path containing spaces AND symlink without spaces - same result

Expected Behavior

HTTP 200 from the app installation check = success → allow background tasks.

Actual Behavior

HTTP 200 logged as "Unexpected response status 200" → fails with misleading "app not installed" message.