Slot drawer polish: retiring slot chips, unknown-stack chip, title fallback

Seen while checking the Slots tab (Automation > Slots) during task 7981. 1. A retiring slot that was never built still shows the `○ Declared` chip in its drawer header beside its Stuck/Destroying tag; show only the destroy state while the slot is retiring. 2. The drawer's stack chip for an unprobed stack reads `? Stack not reported`, which pairs a "?" glyph with words that already say unknown; drop the glyph for the unknown tone, as the table cell now does. 3. A slot with no title shows its occupancy word (`free`) as the Title in the drawer and row, so "free" appears twice; show `—` (or the slot name) when no title is set. Out of scope: slot lifecycle and erase behaviour on nodes; the table cells changed in task 7981. Done means: each item visible in the slot drawer at desktop and phone widths; WorktreePool web tests pass.

Slot drawer: retiring slots show only the destroy tag, unknown stack chip drops "?", free Title reads "—". Quick gate + WorktreePool tests green, visual check done at desktop/phone. PR #6260 queued to merge lane. Follow-up draft #8018.