[Desktop] Tool status title animates width on state swaps (small layout churn)

Description

ToolStatusTitle (the "Gathering context" → "Gathered context" label) writes an explicit pixel width during the text swap, and the CSS transitions that width over 480ms (packages/session-ui/src/components/tool-status-title.css:23). Each frame of that transition recalculates style and layout.

Removing just the width transition keeps the existing crossfade (opacity/filter/transform) and lets the width snap.

Measured in a real desktop instance (1.18.29, via CDP) forcing 125 swaps in 2s:

• before: RecalcStyleDuration +0.081s, LayoutDuration +0.005s
• after: 0.000s / 0.000s

Real-world frequency is low (roughly once per turn, when the context group label flips), so this is a small cleanup rather than a big win. No rest-state visual change.

Plugins

none

OpenCode version

OpenCode Desktop 1.18.29

Steps to reproduce

1. Open a session and run a turn that gathers context (file reads/searches)
2. Watch the "Gathering context" label swap to "Gathered context"
3. In DevTools Performance, style/layout recalculation runs every frame during the 480ms swap

Screenshot and/or share link

No screenshot — no visual difference at rest.

Operating System

CachyOS (Arch Linux), KDE Plasma 6.7.5, Wayland

Terminal

n/a (desktop app)