ci: retire obsolete sync-labels caller

[ss-o]

Summary

Remove only .github/workflows/sync-labels.yml, the dormant caller of the missing z-shell/.github/.github/workflows/sync-labels.yml@main target. This is the fzy canary for z-shell/.github#472. The remaining Trunk workflow, package metadata and every other tracked file are unchanged.

Closes #4. Refs z-shell/.github#472; the cross-repository removal remains unfinished.

Verification

• A removal contract failed before the deletion and passed afterwards: the caller is absent and all 12 remaining tracked files are byte-identical to base 4e5d14bd56d3a33cd52f7e5127bd92d84e7ede57.
• git diff --check passed.
• Actionlint 1.7.12 passed on the retained workflow.
• Repository-pinned Trunk 0.13.0-beta passed check --all --ci --no-progress --verbose in an isolated archive copy. Its output confirms actionlint, gitleaks, markdownlint and prettier coverage.
• The repository contains no functional test suite. The removal does not alter package behavior.

Agent handoff

Merged in d15e979d1cc2be9df92035c061b416db7e814b92. Main was verified to lack the caller, with all 12 retained file blobs and modes unchanged. Issue #4 is closed and both records are Done in Project 28. Rollback is a reviewed revert restoring caller blob b9b9843c5af99539537e3f23ec3ddaf974b4ac76.

[ss-o]

Project 28 triage: filled Item Type CI for the workflow deletion, Impact Low for a dormant missing-target caller, Effort XS for the single-file removal, Priority P2 - Medium for the first deliverable of z-shell/.github#472, and Workstream Administrative for label-management maintenance. Status is now Done after the verified merge. Canonical labels are type:maintenance and area:ci.

The removal contract and full pinned Trunk check passed. All three hosted checks are green on f5794de732540db737c237705778e320d90ffcf0. The current-head review is posted and the merge is verified as d15e979d1cc2be9df92035c061b416db7e814b92, preserving every other tracked file.

[ss-o]

Fallback review under ADR-0026: Copilot request not registered on f5794de

No actionable defects introduced by this change.

The complete diff deletes only the 12-line .github/workflows/sync-labels.yml caller from base 4e5d14bd56d3a33cd52f7e5127bd92d84e7ede57. The review request did not register; its cause remains unconfirmed.

Checklist and verification

• Correctness and scope: passed. The removed file contains only a Tuesday 02:22 UTC schedule, manual dispatch and one reusable job targeting the absent shared workflow. The removal contract failed on the base and passes on this head, proving caller absence and byte identity of all 12 retained tracked files.
• Security and state integrity: passed for the delta. No executable code, permissions, dependencies or secret handling is added. The retained Trunk workflow, package profiles, labels and settings are outside the deletion and preserved.
• Workflow checks: passed. Actionlint 1.7.12 and git diff --check passed on the reviewed head. Repository-pinned Trunk 0.13.0-beta passed its full check in an isolated archive copy, with verbose coverage from actionlint, gitleaks, markdownlint and prettier. Hosted Trunk and CodeQL also passed on this head.
• Traceability: passed. This change satisfies the removal scope of #4 and references z-shell/.github#472 without closing that coordinated work. The final acceptance step is verification of the merged main tree before another repository proceeds.
• Compatibility and application tests: no application code changes; the repository contains package metadata and no functional test suite. Source, interface and loading behavior remain unchanged.
• Recovery: the base caller is retained as blob b9b9843c5af99539537e3f23ec3ddaf974b4ac76; a reviewed revert can restore its exact bytes, including the obsolete reference.

Limits and follow-up

This is a self-review under the written checklist, not an independent human approval or permission to merge. GitHub desktop and narrow-width rendering could not be inspected.

The unchanged .github/workflows/trunk-check.yml:26 still references mutable trunk.yml@main, contrary to the full-SHA policy. A separate fzy maintenance issue is proposed for a verified immutable pin; changing it here would violate #4's preservation scope. Local instruction and review-skill delivery is also absent and needs a separately scoped adoption proposal. This narrow review is not a clean repository-health assessment.