feat(ui): breathe around docked pickers and declutter status glyphs

[tt-a1i]

What

Follow-up polish on the docked pickers and status markers:

• Spacing. The docked picker clung to the conversation above it and floated far above the input. It now gets one empty row of air above the panel and sits one row closer to the editor (bottom margin 6 → 5), so it reads as attached to the input area.
• One glyph per picker row. Rows stacked a selection chevron on the status glyph (❯ ⠿ title). A selected row now keeps its status glyph and borrows the accent tone — running work keeps spinning under selection, and no row ever stacks two markers.
• /ps adopts the shared vocabulary. Terminal picker rows and the detail header used ■ squares; running now spins, done is ✓, failed/timed-out ✗, killed a muted ✓. The subagent and workflow strips align on ✗ for failures, matching the dashboard.
• Quieter spawn marker. The spawn result card's dot becomes a dim +: a spawn adds an agent to the pool — the strip's spinner carries the running state from there.

Verification

• bun run check clean; bun run test: 754 node:test + 29 vitest passing
• Dashboard rendered with a marking theme to confirm single-glyph rows, selection tint, and the air row