feat(ui): right rail as vertical tabs with sideways labels

Replace the right rail's collapsed launcher cards with a vertical tab
strip: one sideways tab per panel, the open panel beside it, at most one
panel open in every HUD layout. The panels' collapsed classes stay the
source of truth; the strip mirrors them and routes every change through
setPanelCollapsed, so persistence and share links are unchanged. Phones
keep the sheet shell.

Five presentations, picked with data-rail-tabs on the rail: cards-down
(default), cards-up, spine, icons and minimal.

The one-owner rule, previously Cyber-only, now applies to every desktop
layout, so the right rail's Tactical auto-collapse retry path is dead and
removed. Escape inside a panel returns focus to the panel's tab.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

style.css

@@ -34,4 +34,5 @@
 @import './src/ui/styles/segmented-control.css';
 @import './src/ui/styles/cjk.css';
 @import './src/ui/styles/mobile-shell.css';
+@import './src/ui/styles/right-rail-tabs.css';
 @import './src/ui/styles/cyber.css';