refactor(ui): remove floating, resizable rail panels

PR #768 bundled a portable-panel windowing system with the Street Level
layer. Remove it so CCTV and Street Level are ordinary docked right-rail
panels again, as on main before the merge.

Removed:
- header drag to float, 8-way edge/corner resize, double-press snap-back,
  dockOnCollapse, command-dock clearance, float hint toast, floating z floor,
  persisted floating geometry and ResizeObserver re-clamping
  (panelPositionControls.js restored to its pre-#768 version)
- src/ui/panelResize.js and its tests, panelDock.test.mjs
- onPanelResized/dockPanel wiring in PanelChrome, the application shell and
  StreetLevelControls (EXPAND/SHRINK no longer docks)
- :not(.panel-floating) guards and .panel-floating/.panel-portable/resize CSS
- qa:panel-resize, qa-panel-resize.mjs, qa-panelDrag.mjs, their tests, the
  CI "Portable panel gate" step, QA_FAIL_ON_RETRY, and the Street Level
  gate's float/resize/dock steps
- floating-panel docs in README, CHANGELOG, CURRENT-STATE, KNOWN-ISSUES

Kept: the Street Level panel as a docked rail panel (share/cockpit/rail
lists, layout controller, rail and Cyber CSS, EXPAND viewer), and the
independent right-rail alignment fix (settledLeftRailTop, 9dde7b4).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/ui/rightPanelRail.js

@@ -69,10 +69,8 @@ export function layoutRightPanelRail({
   // A collapse may schedule one follow-up, which only measures and allocates.
   const isCollapseRetry = pendingCollapseRetries.delete(stack);
 
-  // A floating (lifted-out) panel is not laid out by the rail.
   const panels = [...stack.children].filter(
-    (panel) =>
-      panel.matches('[data-panel-id]:not(.panel-floating)') && !panel.hidden,
+    (panel) => panel.matches('[data-panel-id]') && !panel.hidden,
   );
   if (!hud.visible || hud.variant !== 'tactical') {
     for (const panel of panels.filter((item) =>