fix: whole-repository status survives an unrelated change's invalid branch name (0454)

[danielhanold]

↩ Change 0454 — Whole-repository status must not fail on an unrelated change's invalid branch name

Summary

docket status, maintenance.preflight, and automatic context.implementation selection no longer fail as a whole with external-failed when an unrelated change records an invalid branch: name.

• gitcli's ref-name check now follows git's check-ref-format rules and is exported as gitcli.ValidBranchName.
• The whole-corpus probe (stackBranches) skips names that fail that check, so they count as absent. A child stacked on such a parent reads stack-base-unresolved.
• status reports an error-severity branch-malformed finding on each displayed active change whose branch name is invalid. Its remedy depends on the record: a filled-in repair-identity --adopt-pr-head command if the record has a PR, otherwise a hand edit followed by repository migrate.
• recordedBranch delegates to the same check, so that repair works for names like feat/a:b.
• 0449's integration test now goes through the real Status.

A well-formed name whose probe fails for a real reason still fails the read. Named probes (stackBranchesFor) are unchanged.

Review

Rung: docket-review-standard (every task routed to standard, and the diff is under 1500 lines). No findings.

command: go run ./cmd/docket development test
result: green
head_sha: 5540fa7
ran_at: 2026-09-24T21:16:16Z