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]>

.github/workflows/ci.yml

@@ -67,8 +67,6 @@ jobs:
     timeout-minutes: 30
     env:
       GEV_REQUIRE_ALLOCATION_GATE: '0'
-      # Fail on a missed header press unless the panel itself moved.
-      QA_FAIL_ON_RETRY: '1'
     steps:
       - name: Check out source
         uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4.4.0
@@ -104,10 +102,6 @@ jobs:
       - name: Street Level gate with Mapillary fixtures
         run: npm run qa:street-level:fixtures -- --strict --url http://localhost:4173
 
-      - name: Portable panel gate
-        if: success() || failure()
-        run: npm run qa:panel-resize -- --url http://localhost:4173
-
       - name: Preview server log
         if: failure()
         run: cat preview.log