feat(ios): compact idle composer — one-line per shell when not typing

[boggspa]

What

When the composer text field is not focused (and empty, no draft/queued/attachment), each shell now collapses to a single-line field + model pill + send — like the Claude / Codex mobile composers. Focusing it (or any pending content) expands it back to the full composer: model/approval/guest controls, roster/queued secondary rows, and the telemetry footer rail.

This is the Claude-style idle bar (keeps a model pill), per your pick.

How

• Composer (ComposerView.swift): a @FocusState drives isExpanded = focused || draft || attachment || queued || forced. Idle hides the approval + guest controls (the model pill stays as the compact control). The one-line text + send input row already existed, so no new input layout was needed.
• Host (ThreadDetailView): mirrors expansion via an onExpandedChange callback (composerExpanded), and hides the secondary roster/queued rows + the telemetry rail when idle. attachedBottom now follows expansion so the bar's bottom corners round when the rail is hidden.
• Per-shell skin preserved for free — the shell surface/rim/radius modifiers wrap independently of the inner rows, so Codex stays Codex-skinned, the bubble/capsule shells (Claude/Gemini/Cursor/Obsidian/Alabaster) frame the one-liner, etc.
• Always-expanded (by design): the welcome hero, ensemble composer (its @-direct roster is core context), and the side-chat mini composer (forcesExpanded). A thread with a draft or queued prompt never collapses; focus resets on iPhone thread-switch (the composer instance is reused across threads).

Verification

• swift build + 69 Kit tests + iOS app build (iPhone 17 sim) — all green.
• Recommended on-device pass (visual, can't be unit-tested): cycle the 13 shells via Settings → Composer Shell and confirm the idle one-liner keeps each skin and the bottom corners round. Watch-items from the design map: Codex (#252525 inner module still backs the bar + bottom rounds), Grok (skin holds when the tucked tab disappears), Stub (perforation line on a one-line surface).

Notes / follow-ups

• Compact bar = text + model pill + send (your choice). The pill reuses the existing ProviderModelPicker (already per-shell skinned).
• The side-chat mini composer stays always-expanded for v1; collapsing it (biggest space win in the iPad inspector) is an easy fast-follow if wanted.

🤖 Generated with Claude Code