/autofix-pr fails with 'Claude GitHub app must be installed' despite app being installed

Description

/autofix-pr consistently fails with the error:

Autofix PR failed: can't start autofix —
The Claude GitHub app must be installed on this repository first.
https://github.com/apps/claude/installations/new

The Claude GitHub App is installed and authorized.

Setup (all confirmed)

• Claude Code CLI: v2.1.144
• Claude GitHub App: installed on my company's org (all repositories) and on my personal GitHub account (all repositories)
• App authorization: visible under Settings > Authorized GitHub Apps
• /web-setup: completed successfully ("Connected as [username]. Opened https://claude.ai/code")
• claude.ai/code: works — I can select repos and submit tasks
• gh auth status: authenticated with repo, read:org, gist scopes

Reproduction

1. Be on any branch with an open PR
2. Run /autofix-pr
3. Get the error above

Tested on 2 different repos in the org — same error on both.

Expected behavior

/autofix-pr should detect the installed Claude GitHub App and start monitoring the PR.