Audit Activity and Brains: follow-up polish seen while testing Task 7984

Found while checking Task 7984 on a live stack. Each item is a short requirement; decline any that no longer applies. 1. Audit › Activity: a successful request row's sentence reads the raw `PUT /api/accounts/<uuid>` while its hung line already names "account Weekday rota". Say what happened instead, e.g. "Update account — Weekday rota", and drop the uuid from the row. 2. Audit › Event page: the heading is the same raw method and uuid path, wrapped over two lines; head it with the action and subject, keeping the raw path on the Request tab. 3. Directory › Brains: a new account with no sign-in shows a red ✕ disc and "no credentials" with no next step. Point the row or its ⋯ at Sign in, as the account page does. Out of scope: the Audit API's captured fields; how the roster's enable toggle works. Done means: - Each item shipped or declined with a one-line reason in the PR, with web unit tests where behaviour changed. - Screenshots at 1280px and 390px of each changed surface. Required checks: ./dc check full

Shipped all 3 items: Audit rows and event heading say "Update account — Weekday rota" (no uuid), and Brains ⋯ offers Sign in for an account signed in nowhere. Quick gate, unit tests and e2e green; visual check at 1280/390 done. PR #6261 queued in the lane; follow-up draft #8017.