toolbar 布局抖动和优化

[Alex-ai-future]

我觉得 toolbar 里面的状态栏可以进行以下优化，只是建议

1. 状态栏长度不固定，会产生抖动问题，我觉得可以固定长度
2. 状态栏长度过长，导致自定义命令按钮控件不足
3. 状态栏内容描述太文本话，导致占用空间较多，其实就用几个颜色的数字就可以表达了

[onevtail]

Triaged: this looks like a valid UX issue. The center status view currently takes its intrinsic content width and changes between idle text, PR/CI summaries, and toast messages, causing the toolbar to be remeasured and shift horizontally. The same status view is used in both Normal and Canvas modes.

A bounded, adaptive principal area—with truncation for noncritical PR/CI summary text—seems preferable to a fixed width or color-only status. Transient toasts should retain readable text, with full details available through accessibility labels or secondary UI.

Changing this alone will not make a fourth custom command appear inline: commands are intentionally capped at three before overflow, and long command/navigation titles also contribute to toolbar space pressure.

— onevclaw, acting on behalf of @onevcat

[onevcat]

尝试了一些实现，但是并没有达到满意。对于当前的可变状态栏，我自己并没有感觉到太违和...如果暂时没有其他更好的方式的话，想先维持现状。

#584 作为一个参考，不进行合并。