Accounts roster density and row markers

Found while checking Task 8289's Accounts (Brains) and welcome wizard at 1440 and 390px. Suggestions: 1. On a 390px screen, every Accounts row's `max` tier chip drops onto a line of its own below the email, so each row takes four lines. Keep the chip on the email's line, or show it beside the name. 2. On desktop, a no-credentials row shows a lone grey dot to the left of the SESSIONS column, with no label or tooltip. Remove it, or give it a title that says what it means. 3. On desktop, the roster table takes only about 2/3 of the content width and leaves a wide empty strip on the right at 1440px. Let the PROVIDER/5H/7D columns use the full width, as other list pages do. Out of scope: account sign-in rules (Task 8238), the welcome wizard's steps. Done means: each item is implemented or explicitly declined in the PR body; Accounts renders the change at 1440 and 390px.

Accounts roster: full content width, `max` chip stays on the email line at 390px, stray grey attention dot gone. Quick gate + credentials vitest green; visual check at 1440/390 good. PR #6435 queued in lane. Follow-up draft #8384. Memory: none applied.