feat(task-board): file a task on the board when a PR is published

[rafavalls]

Summary

Stack 3 of 3 — targets rafavalls/task-pill-session-tabs (#6425), not main.

Publishing from a chat now records the work on the board: if the thread has no linked task, useRecordPrOnBoard promotes it to one and links the PR, so published work is never untracked. Both the GitHub publish dialog and the CMS publish action go through it.

The OpenInBoardButton header action is deleted — TaskCrumb (added in the parent PR) now carries the link back to the board, so the button was a second, redundant affordance. Its i18n keys go with it.

Testing

tsc --noEmit clean on apps/web.

Notes for the reviewer

Small on top of its parent (+97/−60). Worth checking the promote path is idempotent under a double-publish, and that a publish failure doesn't leave a task filed with no PR linked.

🤖 Generated with Claude Code

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Summary by cubic

Automatically files a board task when a PR is created from chat or the CMS. Previously, publishing or submitting for review did not create/link a task; now we promote the thread to a task (if needed) and link the PR so shipped work is tracked. Removes the header Open in Board button; TaskCrumb is the single navigation affordance.

• New useRecordPrOnBoard runs on publish and submit-for-review from both the GitHub publish dialog and CMS actions; it promotes the thread to a task, links the PR, and shows an “Added to board” toast with an Open action.
• Idempotency: check double-publish does not create duplicate tasks and that the PR link updates correctly.
• Status mapping: merged publish sets status to “in_review”; submit-for-review sets “in_progress” — confirm this is intended.
• Failure isolation: errors filing the task are swallowed so publishing isn’t blocked; the board will reconcile on next load.
• UI cleanup: removes OpenInBoardButton and its i18n keys; navigation back to the board now lives only in TaskCrumb.

^{Written for commit 1838b57. Summary will update on new commits.}