feat(tui): declutter round 2 — /settings (71 rows), /setup providers (flat 30+), /fleet naming

Founder: "de. clutter. it's so busy."

Round 1 landed in 0.9.13 (pre-session metrics row removed — `684bbdc1d`; launch MCP block consolidated; launch-card dissolve real). What remains:

## 1. `/settings` — 71 rows

One flat scroll for everything. Candidate: group by area (model / approval / UI / MCP / advanced), fold the rare ones behind one level.

## 2. `/setup` providers — flat 30+

No grouping or search; every provider is a peer row.

## 3. `/fleet` — naming

An 11-member default team, and setup role labels disagree with roster names (carried from the 2026-09-11 handoff §5c.4).

## 4. Composer chrome before the first message

The metrics row now hides until a session exists, but the posture row (`▶▶ Full Access · operate · ⏱ 2 scheduled`) still paints pre-session — there is no idle gate on it (`crates/tui/src/tui/ui/frame.rs:1736`; only the metrics row is gated at `:1374-1384`). Decide whether that row stays (it tells the user their posture before they type) or joins the idle gate.

## Notes

Founder-directed; none of these are defects. Row counts come from the 2026-09-11 handoff — re-count at implementation time. Composer items are one screen, so they can ship as one slice or split per surface.

Start with crates/tui/src/tui/ui/frame.rs:1736 and compare it with the metrics idle gate at :1374-1384. Inspect the /settings, /setup provider, /fleet, and composer surfaces, and review the 2026-09-11 handoff §5c.4; re-count rows and clarify the intended grouping, provider navigation, fleet naming, and posture-row behavior before implementation.

Written by the indexing model from the issue text.