ultraplan: 'Claude GitHub app must be installed' despite app being installed

Description

/ultraplan consistently fails with:

ultraplan: cannot launch remote session —
The Claude GitHub app must be installed on this repository first.
https://github.com/apps/claude/installations/new

Environment

• Claude Code CLI (latest, macOS)
• GitHub account: bnm-git
• Repo: bnm-git/auto-yoast (private)
• Claude GitHub App: installed on bnm-git account with "All repositories" access
• App confirmed: claude by anthropics (ID: 1236702)
• Waited 20+ minutes after installation, same error

Steps to Reproduce

1. Install Claude GitHub App on account via https://github.com/apps/claude/installations/new
2. Select "All repositories", save
3. Confirm app appears in Settings → Integrations → Applications
4. Run /ultraplan <prompt> in Claude Code CLI

Expected

Remote session starts, web link appears.

Actual

Error about missing app installation, despite app being installed.

Diagnostics

• gh api /user → bnm-git ✓
• gh api /repos/bnm-git/auto-yoast → exists, private, main branch ✓
• curl https://api.github.com/apps/claude → slug: claude, owner: anthropics, id: 1236702 ✓
• App visible in GitHub Settings → Applications with correct permissions ✓
• Git remote: git@github.com:bnm-git/auto-yoast.git ✓