SRE-715: Add reusable workflow enforcing Linear issue ID in PR titles

[TimDiekmann]

Summary

• New reusable workflow preflight-pr-title.yml that fails when a PR title is missing a Linear issue ID (e.g. H-1234, BE-5678, SRE-715) in the prefix segment (text before the first :).
• Mirrors the prefix-parsing convention already used by preflight-todo-comments.yml, so both checks key off the same set of IDs.
• Skips bot-authored PRs by default (pull_request.user.user.type == 'Bot' — covers hash-worker[bot], dependabot[bot], and any future GitHub App). Additional human logins can be exempted via the ignored-actors input.
• Failure case prints a self-explanatory summary in $GITHUB_STEP_SUMMARY (current title, expected format, examples).
• Self-PR (changes to the workflow file itself) triggers the workflow via the paths: filter — this PR's title is intentionally missing an ID so the workflow can fail on itself as a smoke test. ✨

Once stable, the next step is wiring this as a required status check via workflow_call in consumer repos.

Test plan

• Workflow run on this PR fails (no Linear ID in title)
• Re-title to include the ID (e.g. SRE-715: …) and re-run → passes
• Verify summary message is helpful
• Confirm pull_request_target path still works once wired into a consumer repo

[cursor]

PR Summary

Medium Risk
Introduces a new PR-gating GitHub Actions workflow that can fail human-authored PRs based on title format, potentially blocking merges if misconfigured. Uses pull_request_target/merge_group triggers but only reads PR metadata, keeping security risk low.

Overview
Adds a reusable GitHub Actions preflight (preflight-pr-title.yml) that fails human-authored PRs when the PR title prefix (before the first :) does not contain at least one Linear-style issue ID (e.g. H-1234).

The workflow supports workflow_call with an ignored-actors allowlist, automatically skips bot authors, and writes a clear pass/fail message to GITHUB_STEP_SUMMARY showing the expected title format and detected IDs.

^{Reviewed by Cursor Bugbot for commit 779df27. Bugbot is set up for automated code reviews on this repo. Configure here.}

[augmentcode]

🤖 Augment PR Summary

Summary: Introduces a reusable GitHub Actions workflow to enforce that human-authored PR titles include a Linear issue ID.

Changes:

• Added .github/workflows/preflight-pr-title.yml to validate PR title prefixes (segment before the first :) for IDs like H-1234/SRE-708.
• Skips checks for bot-authored PRs and supports an optional ignored-actors allowlist.
• Emits a clear pass/fail explanation into $GITHUB_STEP_SUMMARY with examples.
• Includes a paths filter so edits to the workflow can self-test on PRs.

Technical Notes: Uses simple shell parsing (prefix extraction + case-normalized regex match) and keeps permissions scoped to contents: read.

_{🤖 Was this summary useful? React with 👍 or 👎}

[augmentcode]

Review completed. 1 suggestion posted.

Comment augment review to trigger a new review at any time.