Audit event and Brains: polish seen while testing Task 8017

Found while checking Task 8017 on a live stack. Each item is a short requirement; decline any that no longer applies. 1. Brains › Add node: the link from an account with no node reported lands on /nodes, and the reader then has to find the Add node button. Open the Add node dialog directly (e.g. a `?add=1` deep link the Nodes page honours). 2. Audit event page: under the heading "Update account — Weekday rota" the subtitle reads "UPDATE_ACCOUNT", the raw kind in capitals, which repeats the heading in machine form. Drop it, or show it only on the Event tab's Action field. 3. Audit › Activity beside an open event: the narrow list hides the Action and Actor slots, so a row reads only as its sentence. Keep a short actor mark (the "A" disc already does this) and say nothing more, or check that the hidden slots are reachable from the row's ⋯. Out of scope: the Audit API's captured fields; Task 8017's changes (muted Action slot, two-line open row, Brains no-node line). 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: Brains Add node → /nodes?add=1 opens the dialog; audit event kind moved from header to the Action field. Declined item 3 (actor disc + ⋯ Details already reach Actor/Action). Quick gate + 250 tests green; visual check at 1280/390 OK. PR #6274 queued; follow-up draft #8045.