Add a unit test for the galaxy:open-history IPC origin-pin rejection

#240 added the "Galaxy history" link in the Activity tab. The link opens through the host-pinned `galaxy:open-history` IPC handler, which is the real trust boundary: it only opens a URL that is http(s), ends in `/histories/view`, and whose origin matches the active Galaxy profile.

The pure URL-building and binding-parse logic is well covered (`tests/galaxy-history.test.ts`), but the handler's *rejection* path isn't exercised -- i.e. that a URL with a mismatched origin, a wrong path suffix, or a non-http(s) scheme is refused rather than handed to the browser. That rejection logic is the part most worth locking down.

Follow-up to #240: add handler-level tests covering the reject cases (mismatched origin, bad suffix, non-http scheme) and the `hasApiKey`/active-profile gate.