Close GitHub issues once their Bugsnag errors are fixed

**Objective:** For the Bugsnag project `{project-name}`, find errors marked fixed in the last `{lookback-days}` days (default 14) whose GitHub issue is still open, and close those issues with a comment once the user confirms.

**Step 1: List fixed errors in Bugsnag**

Call `bugsnag-get-error` with `project-name` set to `{project-name}`, `status` set to fixed, and `last-seen.from` set to `{lookback-days}` days before today. Record error-id, error-class, message, last-seen-date and error-url.

**Step 2: Find their issues on GitHub**

For each error, call `github-get-issue` with `title.contains` set to the error-id and `status` set to open. Keep only issues whose title contains `[Bugsnag <error-id>]`. Do not fall back to matching by error-class here: closing an issue on a fuzzy match is how the wrong issue gets closed.

**Step 3: Confirm**

Show a table of the pairs: error-class, error-id, last-seen-date, issue-number, issue title, assignee. Ask the user which to close (all, some, or none). Wait for an explicit answer.

**Step 4: Close the confirmed issues on GitHub**

For each confirmed issue, in this order:

1. Call `github-add-issue-comment` with `issue-number` and a `body` saying the error was marked fixed in Bugsnag, with its error-url and last-seen-date.
2. Call `github-update-issue` with `issue-number` and `state` set to closed. Pass nothing else, so no other field changes.

**Step 5: Report**

The issues closed, the ones skipped, and any failures.

**Rules & Guidelines:**

* `bugsnag-get-error` is on the bugsnag server. `github-get-issue`, `github-add-issue-comment` and `github-update-issue` are on the github server.
* The only write tools this prompt may call are `github-add-issue-comment` and `github-update-issue`, and only for the issues the user confirmed. Do not call any Bugsnag Action tool, such as `bugsnag-open-error` or `bugsnag-fix-error`, and do not call `github-lock-issue`.

**Validation:**

* If no errors were fixed in the window, say so and stop.
* If a fixed error has no open issue, it needs nothing; count it but do not list it.
* If the comment succeeds but the close fails, report the issue as commented and still open. Do not post the comment again on retry.