Directory at phone width: Agents tab wrap

Found while screenshotting Directory > Machines > Brains at 360px (Task 6685): 1. At 360px the Directory strip (Projects, People, Machines, Secrets, Agents) puts "Agents" alone on a second line; scroll the strip or tighten it so every tab sits on one line, as Task 6667 does for the Machines strip. 2. An expanded Brains account's per-node child rows still reserve the 99px provider slot on a phone, although the account line above already names the provider; gate it off on the phone band (the `phone` slot gate from Task 6685) so the node name gets the width. 3. On a phone the Brains 5h column (92px) shows only "—" on every row with no credentials; consider narrowing it on such rows or giving the dash's width back to the title, without breaking column alignment. Out of scope: desktop layout of these surfaces; server behaviour. Done means: each item changed or declined with a one-line reason in the PR body, with a 360px screenshot per changed surface; `./dc check full` green.

All 3 items changed: Directory strip one line at 360px; Brains node rows drop provider slot on phone; dash-only 5h narrows to 32px. 360px visual check clean. Local full gate green except api-unit (host contention); merge lane gate merged #5634. Deploy superseded. Draft #6725 filed.