Put Bugsnag errors on the BugHerd board, linked both ways

**Objective:** Log Bugsnag error `{error-id}` as a task in the BugHerd project `{project-name}` and link the two.

How the two systems are linked: a BugHerd task created from a Bugsnag error carries "bugsnag:<error id>" in its external-id, and the Bugsnag error is linked to the task's admin-link with `bugsnag-link-error-issue`.

**Step 1: Read the error**

Call `bugsnag-get-error` with `error-id` set to `{error-id}`. If it is not found, stop. Call `bugsnag-get-event` with `error-id` and `max-records` 20 and take the most common request-url as the page.

**Step 2: Check for an existing task**

Call `bugherd-get-projects` with `name.contains` set to `{project-name}`. If nothing matches, say so and stop. If several match, list their names and project-id values and ask which one; do not guess. Then call `bugherd-get-tasks` with `project-id` and `external-id` set to "bugsnag:{error-id}". If one exists, report it and stop.

**Step 3: Prepare the task**

* description: "<error-class>: <message>", then the page, the context, events and users so far, first and last seen, release stages, and the error-url.
* severity: critical when the Bugsnag severity is error and it affects more than 100 users; important when severity is error; otherwise normal.

**Step 4: Confirm, then write**

Show the task and wait for an explicit yes. Then:

1. Call `bugherd-add-task` once with `project-id`, `description`, `severity` and `external-id` "bugsnag:{error-id}".
2. Call `bugherd-get-tasks` with `project-id` and `external-id` to read back the task number and admin-link.
3. Bugsnag write tools need the Bugsnag project-id, which `bugsnag-get-error` does not return: call `bugsnag-get-project` with `name` set to the error's project-name to get it. Then call `bugsnag-link-error-issue` once with `project-id` (the Bugsnag one), `error-id`, `issue-url` set to the admin-link and `verify-issue-url` false.

**Step 5: Report**

The task number and admin-link, and whether the Bugsnag link was added.

**Rules & Guidelines:**

* Tools named bugherd-... are on the bugherd MCP server; tools named bugsnag-... are on the bugsnag MCP server. If either set of tools is missing, say which server is not connected and stop.
* The only write tools this prompt may call are `bugherd-add-task` and `bugsnag-link-error-issue`, each once, after the user confirms.
* Do not change the error's status or severity.

**Validation:**

* If `bugherd-add-task` fails, show the error and do not touch Bugsnag.