Check whether a GitHub deploy introduced new Bugsnag errors

**Objective:** Check whether the deploy from GitHub Actions run `{run-number}` on branch `{branch}` (defaults: the latest successful run, on main) introduced new errors in Bugsnag.

**Step 1: Find the run on GitHub**

Call `github-get-workflow-run` with `branch` set to `{branch}` (default main) and `conclusion` set to success. If `{run-number}` is given, also filter by `run-number`. Otherwise take the run with the latest created-date. If several workflows ran for the same commit, list their names and ask which one is the deploy, then stop.

Record name, run-number, sha, created-date, commit-author-name and commit-message.

**Step 2: Find the matching Bugsnag release**

Call `bugsnag-get-release` with `release-date.from` set to the run's created-date. Keep the releases whose source-control-revision equals the run's sha, or is a prefix of it. There may be one per Bugsnag project; keep them all.

**Step 3: Look for new errors in each matched project**

For each matched release, call `bugsnag-get-error` with `project-name` set to that release's project-name and `last-seen.from` set to the release-date. Keep errors whose first-seen-date is on or after the release-date.

**Step 4: Report**

* The deploy: workflow name, run number, branch, sha, author, first line of the commit message.
* Per project: release app-version and stage, errors-introduced-count, unhandled-sessions-count against total-sessions-count, and the new errors (error-class, severity, events, first-seen-date, error-url), most events first.
* A one-line verdict: clean, new handled errors only, or new unhandled errors.

**Rules & Guidelines:**

* `github-get-workflow-run` is on the github server. `bugsnag-get-release` and `bugsnag-get-error` are on the bugsnag server.
* This is read-only. Do not call `github-rerun-workflow-run`, `github-cancel-workflow-run`, `github-add-issue`, `bugsnag-create-error-issue` or any other Action tool. If new errors warrant an issue, suggest the `file-github-issue-for-error` prompt instead.

**Validation:**

* If no successful run matches, report the most recent run on the branch with its conclusion and stop.
* If no Bugsnag release carries the sha, say that the build was not reported to Bugsnag with source control information, and stop rather than matching by date alone.
* Errors seen within the first few minutes of a release can be old errors on a new version. Only count an error as new when its first-seen-date is after the release-date.