[abretonc7s]

Description

Concurrent slot prepares failed with fatal: Cannot rebase onto multiple branches while updating one shared skill source. Serialize the existing git pull --ff-only per checkout. Separate checkouts stay parallel, and failed updates still refuse stale installation.

The full-catalog CI audit also required shortening an existing oversized TypeScript skill description. Its body and references are unchanged.

Type of change

• Bug fix

Testing

• 76/76 tests pass in 22.35s; changelog, Bash syntax and full-catalog audit pass. Exact-head CI is green.
• Three real-Git regressions. Unchanged main reproduces the exact reported error.
• Two concurrent authenticated macpro prepares, Haiku-configured private slots: eee4734b-357a-476e-a6a9-374ec61936d6 and 0e91148a-c813-4557-aa33-41b94e2ba4a6. Both returned prepared=true, installed the expected revision and were cancelled. Hook concurrency 2; Git-pull concurrency 1. No worker dispatched.
• Original proof wrapper failed afterward on a wrong response-field assertion. A separate saved-case audit verifies raw replies, Git state and installed files; no cases rerun.

Preflight incident: before the private socket parent existed, an import sent two cosmetic tmux option writes to the existing shared server. No session lifecycle command ran. Prior option values were not captured; no restoration claim. Actual prepares used a corrected explicit private-socket fence, and owned cleanup passed.

F200. No selection, branch-reset or installer policy changes. Existing callers need the normal post-merge source/package rollout.