fix(board): preserve column and assignment save ownership

[Chris0Jeky]

Column writes could start after their board screen had closed, and a removed column lane could clear the navigation guard for an assignment save already sent to the server. This integrates the repaired column lane with PR #3313's request-owned assignment registry, preserving every source commit.

• Column create/update/delete/reorder serialize per board. An explicit BoardView visit and logout generation reject retired queued work before transport and suppress stale UI. A successful old write can refresh only an active reopened visit in the same session.
• Assignment saves own independent operation tokens in BoardCanvas. Removing a field/lane does not release a pending PUT; each request releases its token on settlement. Multiple saves aggregate, and replacement/unmount retires old tokens.
• Paper/Legacy skin changes keep the column visit. Column visit retirement does not reset the assignment registry. Reconciliation installs columns and the delete cascade under one ownership guard.
• Fixes three array-identity assertions to compare the actual Vue reactive arrays while retaining complete content assertions.

Validation at final integration head 7ed57325cf03ce1548418242531c2ae4125efb8a, based on 308434f523a31864a43672d68ad5a315121c5dae:

• Initial ten route/session regressions failed before the column fix; the expanded fourteen-case module passed afterward. Column/route seam: 143 passed before three supplemental cases. Assignment source seam: ten passed.
• Both source reviews and the final combined integration review found no HIGH/CRITICAL blockers. Nonblocking stalled-column-lane recovery is tracked in frontend: define recovery for stalled column mutation lanes #3357.
• Typecheck, build, lint (11 existing warnings), docs governance and doc links passed.
• Final full frontend: 516 files, 7,362 passed and three existing skips. Targeted Chromium: four passed (column reorder persistence, board switching, and delayed assignment-save behavior in Legacy and Paper).
• Backend tree exactly matches main; the preceding trust integration's full backend result is 10,249 passed, one existing skip. This PR changes no backend/API/schema.

A submitted server write cannot be cancelled by retiring its UI owner. Broader card/comment/label/board lifetime work remains #3306, and shared-loading arbitration remains #3305. No human approvals in OUTSTANDING_TASKS.md are inferred or closed.

Closes #3314
Closes #3311

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-20T22:19:48.226240Z	a1264ab	Draft marked ready

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[chatgpt-codex-connector]

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Reviewed commit: a1264abc84

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[Chris0Jeky]

Required run 35766201480 at head 7ed5732 reached the Windows API test step's 45-minute timeout. The diagnostics show 1,713 passed tests and continued progress immediately before cancellation. The last observed assignment concurrency case started only 2.5 seconds before cancellation; there is no assertion failure or established hung test. The missing TRX and timing artifact are downstream consequences.

Runner context reports four CPUs, 17.17 GB total memory and 13.7 GB available before execution, with no OOM signal. The backend tree still matches the already-qualified parent. One rerun of the same-head Windows job is now underway to distinguish a reproducible runtime problem from run-to-run variation. This is not a flaky classification, and the PR remains unmerged until the required gate passes.

The failed log and six diagnostic artifacts are preserved locally under the session-mutations worktree's .runtime/parent-windows-api-artifacts. A bounded Luna inspection supplied this classification; it performed no code changes or process actions.

[Chris0Jeky]

Merged and reconciled: #3315 landed at 346b3c7, preserving the assignment source #3313 and column ordering history. Required CI 35766201480 attempt 2 passed at head 7ed5732. The original Windows API timeout was investigated; the unchanged-head rerun passed, while the original runtime cause remains unresolved. It is not classified as flaky.

Local final proof was 7,362 frontend passes, three existing skips, build/typecheck/lint/docs checks, four passing Chromium journeys, and clean independent source/integration reviews. #3314 and #3311 are closed; both PRs and both issues are Done with their original priorities. The post-merge checkpoint found zero unresolved review threads and no new substantive feedback on either PR.

The owned integration claim is released. Before removing the completed worktree with plain git worktree remove, all 27 .runtime files and the browser result were copied and hash-verified under C:/Users/jekyt/source/Taskdeck/.runtime-codex/2026-09-22-hard-impact/board-integrated/. The cleanup manifest records exact paths and hashes. Existing worktrees and primary user edits remain untouched. OUTSTANDING_TASKS.md retains the separate owner actions; descendant #3358/#3359 maintainer review is still pending.