fix: apply the review items for #689 at merge

Clamp the stored toolbar width to MIN_WIDTH in apply() and step the arrow keys from the width on screen, so a drag to the window edge or a held ArrowRight no longer stores a negative width or leaves an ArrowLeft dead zone (browser test added)
Drop Escape as a reset key on the handle: the global capture-phase Escape handler already closes every panel on it (static pin added)
Say in the changeset, the wiki and the densityFor comment that the percentages go at the narrowest step in the Compact style only, and drop Escape from the changeset

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/wiki/The-Dashboard.md

@@ -180,9 +180,9 @@ Hiding System Stats or Plan Usage still hides them in every style.
 
 The line between the session tabs and the toolbar is a handle: drag it right to narrow the toolbar
 (it wraps onto a second line and the usage readings shed their labels, then their provider names,
-then their percentages), left to widen it. Arrow keys resize it, and double-click or Home resets it.
-It stops at the widest reading, the width is kept per device, and it is not shown on phones, in the
-sidebar layout, in the vertical rail or in a solo window.
+then, in the Compact style, their percentages), left to widen it. Arrow keys resize it, and
+double-click or Home resets it. It stops at the widest reading, the width is kept per device, and it
+is not shown on phones, in the sidebar layout, in the vertical rail or in a solo window.
 
 New header controls never appear on phones. Phone layout is deliberately minimal and is
 covered in [Mobile Guide](Mobile-Guide).