Task pane: org-filter not-found and breakpoint re-reads

Found during Task 7215's visual check of a deep link to a task hidden by the org filter (`/tasks/<id>?orgs=<other>`). 1. On a phone (390px) the "Hidden by the org filter" pane shows no org chip or name: the OrgScopeBar lives in `<main>`, which the pane hides. Name the active filter (e.g. "Hidden by the org filter (Org B)") so the reader knows which filter to clear. 2. Resizing across the phone breakpoint while a task pane is open remounts the page and re-reads `GET /api/tasks/{id}/page` (seen in the trace: one extra `/page` per crossing). Keep the pane mounted, or reuse the landed read, across the layout switch. Out of scope: the org filter's semantics; the cold-load 404 handling (Task 7215). Done means: - At 390px the hidden-task pane names the active org filter. - A viewport crossing the phone breakpoint with a task open issues no new `/page` request, as seen in a Playwright trace.

Hidden-task pane now names its filter ("Hidden by the org filter (Org B)"); a remount across the split width reuses the landed read, with no new /page (trace + e2e). Merge lane merged #5924 after its full gate; deploy green. Follow-up draft #7303.