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]>

docs/KNOWN-ISSUES.md

@@ -57,9 +57,9 @@ Related keys (current versions):
 - Panel collapsed state: `godsEyeView.v6.panelCollapsed.<panel-id>` — `'0'` open,
   `'1'` closed, absent means the panel's own default. A view opened from a share
   link ignores the stored value entirely.
-- Panel positions: `godsEyeView.v8.panelPos.<panel-id>` — written only for a
-  floating portable panel (CCTV, Street Level). Deleting it, or double-clicking
-  the panel header, docks the panel again.
+- Panel positions: `godsEyeView.v8.panelPos.<panel-id>` — the versioned name for a
+  stored position. The current layout writes none, so deleting one changes
+  nothing.
 - CCTV calibration: `godsEyeView.cctv.calibration.v2`
 
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