fix(labels): bind async commits to their board

[Chris0Jeky]

Summary

Hardens the selected-board label collection against late responses, same-board refreshes, overlapping writes, and session changes:

• stale reads cannot overwrite a newer read or confirmed mutation;
• board-visit generations distinguish A→B→A and logout/login even when the board id repeats;
• same-board detail refreshes may receive a successful in-flight write into their newly installed label array;
• successful writes from an older visit trigger a bounded authoritative reconciliation only when that same board is currently reopened;
• same-label update/delete requests are serialized because the API has no revision precondition;
• queued writes recheck the initiating visit before transport starts, so pre-logout intent cannot run under a later session;
• the first, unqueued write starts transport synchronously in the initiating call stack;
• create deduplicates by stable id.

Tests

Focused deferred-promise coverage includes late fetch/create/update/delete after navigation, overlapping reads, stale reads after mutations, same-board refresh before write settlement, A→B→A reconciliation, reverse-settling same-label writes, and cancellation of queued work after session replacement.

Verification

Exact head: ba2eba81e08aa4a221dd26920f86404580242baa

• Smart CI Self-Test run 35531548034: success.
• CI Extended run 35531548246: success.
• Required CI run 35531548208: success across frontend lint/typecheck/build/full tests on Ubuntu and Windows, backend unit/API integration on Ubuntu and Windows, architecture, migrations, containers, dependency/SAST/secret scans, docs governance, worktree contracts and E2E smoke.
• Both Codex findings are addressed with dedicated regressions, replied to, and resolved.
• Fresh exact-head diff review completed; no DTO, route, migration, control-plane or canonical-document changes.

Closes #3301

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-20T21:54:12.501043Z	ba2eba8	Draft marked ready

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[chatgpt-codex-connector]

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Reviewed commit: 58fa07b027

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