chore(gha): add linear.yml GitHub workflow

[ms-bot]

Why is this needed?

This pull request has been created by a robot to add the linear.yml GitHub workflow.

[Copilot]

Pull request overview

Adds a new GitHub Actions workflow intended to integrate pull request activity with Linear (title compliance checks, bot PR → Linear issue creation, and Linear state checks) as part of the repo’s CI policy automation.

Changes:

• Introduces a new Linear workflow triggered on pull_request events and merge_group.checks_requested.
• Runs mobsuccess-devops/github-actions-linear for PR title compliance, bot PR issue creation, and Linear state validation.

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[maximus-agents]

🤖 fix-approve-merge

Outcome: BLOCKED ⛔
Head commit: ff7a93ae89e04d32a62408af6d01fa3443cd8ae3

The generated workflow's Linear check still fails during action preparation with Unable to resolve action mobsuccess-devops/github-actions-linear, not found; the action repository is private and the fresh rerun was rejected with 403 Resource not accessible by integration, so approval and auto-merge were not performed. Existing Copilot requests remain resolved with upstream-policy replies: runner label thread, action pinning thread 1, action pinning thread 2, action pinning thread 3, and upstream-policy reply. The generated .github/workflows/linear.yml must not be edited in this PR.

Next: An administrator must grant this repository's Actions integration access to the private github-actions-linear action, or repair its visibility/sharing policy, then rerun Linear and this mission.