Tasks board and task page: one clean layout

Goal: /tasks and /tasks/:id read cleanly at a 1440px split pane, at 1024–1366px and at 390px. No fields overlap, no control sits detached, and the header looks the same for every task. The items below are goals, not literal steps: meet their intent, and decline any already met with a reason. Task 6817 partly fixed item 1, so verify before rebuilding it. Board (/tasks) 1. The "Search tasks" field and the quick-add composer never overlap. They sit on separate rows, and only one of the field's label and placeholder shows at a time. The toolbar buttons share the search line, which is what e2e/tasks-feed.spec.ts:811 and e2e/tasks-mobile.spec.ts:207 expect. Check with a task open in the split pane at 1440px, at 1366px, and at 390px, where the toolbar must not draw a divider through the search field. 2. The composer placeholder ("Type a task and press Start…") fits on one line at 390px, at the row's text size. Shorten it. Task page and side pane (/tasks/:id) 3. The status pill sits in one place whatever the title length. 4. The breadcrumb never ends in a trailing "›". Child stage tasks and top-level tasks show the same crumb set. 5. Details: - Past a short spawn window, the Runner row says there is no session instead of "starting… · 1h 12m". - The State select uses the dense height, so its row lines up with Persona and Priority. 6. Tags card: hide it, or reduce it to the Re-tag button, when the org has no tag groups. On a phone, the sentence comes before the button. 7. The "Unverified done" banner is compact enough that it does not push the field grid below the fold in the split pane. 8. Artifacts and rating: - Hide the detached "rating unavailable" caption when there is no rating. - Space the artifact version badge ("v2") and dim it like the size·age metadata. - On a phone, the viewer's Download button fits beside the filename (icon-only) instead of taking its own row. Out of scope: task states and transitions; API changes. Merge-lane task pages are covered by the Merge lane console task. The floating assistant button and PageHeader internals are covered by the Console shell task. Done means: - A screenshot of each surface at 1440px (split pane), 1024px and 390px, judged readable. - The e2e specs above pass. - `./dc check full` is green. Consolidates drafts 6872, 6878, 6914, 6828, 6888, item 1 of 6881 and item 2 of 6915 (Task 6937).

Tasks board + task page layout fixed across 1440 split/1024/390 (all 8 items; item 1 mostly pre-met by 6817). PR #5746 merged (33239e2), Jaah Deploy green. Visual check done, all surfaces readable. Lane went off before its full gate; local full gate on develop was green except one merge-lane API test, a 6941/6722 clash develop has since fixed (28/28). Follow-up draft 6974. Deferred: 2 docs screenshots still show the old placeholder.