Move the composer strips out of the pop-out drag region

[OutThisLife]

Summary

The micro-action pills, the status stack, and the composer.underside strip all rendered inside the composer root. The pop-out drag region is an absolute inset-0 child of that root, so everything alongside it was inside the grab area by construction — hovering a pill hatched the composer, and a press landing between two badges started a peel-out drag.

That was getting patched at the gesture rather than the structure: a composer-no-drag exclusion in gestureTargetOk, a matching guard on the double-click toggle, and a strip juggling z-index and pointer-events to climb back over a region painting on top of it. Each fix traded away a bit of the vertical band the composer is actually grabbed by.

This adds a dock column that owns the composer's position and stacks its children in flow, bottom-anchored:

composer-dock
├── micro-action strip
├── status stack
├── composer            ← drag region lives in here, and only here
└── underside strip

The strips are siblings of the composer rather than children, so landing in the grab area is impossible instead of excluded. gestureTargetOk and the double-click handler revert to their pre-existing form, and the shared strip constant drops to a bare flex row.

Two things fall out of the move:

Alignment stops needing a magic number. The strips sat in different containing blocks — one in the stack's absolute lane resolving against the root's padding box, one in the root's content box — and the root carries padding-inline: 5px for the grab margin. That was the 5px the pills hung left by, and the pl-[0.3125rem] in #73741 was compensating for it. One parent and a shared px-[5px] line both strips up with the surface directly.

The status stack stops measuring itself. It published --status-stack-measured-height only because it was out of flow and the composer's measurement couldn't see it. As a dock child it's covered by the dock's own height, so the var, its ResizeObserver effect, and the detached-node cleanup that effect needed all go — thread clearance now reads one number instead of summing two. Note this also removes surface-var-lifecycle.test.tsx: it guarded a real regression (a stale clearance written to :root from a detached node), but the mechanism it tested no longer exists, and the bug class is now structurally unreachable.

Net −139 lines.

Test plan

• tsc --noEmit clean, eslint 0 errors
• 28 files / 221 tests pass (vitest run src/app/chat/composer src/app/chat/surface-vars.test.ts from apps/desktop)
• Pills, status stack, and underside all verified outside the composer root
• Pills, underside chip, and composer surface share one left edge with no compensating padding
• Composer still drags and double-click-to-float still works from the margin around the surface, with the full vertical band intact
• Pills remain above the status card and the billing banner

[github-actions]

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ℹ️ Info

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