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/styles/street-level.css

@@ -125,7 +125,6 @@ button.sl-status:focus-visible {
   pointer-events: none;
 }
 
-/* In a resized window only this block scrolls; the viewer keeps its room. */
 .sl-settings {
   display: flex;
   flex-direction: column;
@@ -476,52 +475,6 @@ button.sl-status:focus-visible {
   display: none;
 }
 
-/* ── Floating window ─────────────────────────────────────────────────────── */
-/* A dragged window keeps its natural height, so bound it to the viewport:
-   the rail's max-height: 100% does not bind an auto-height parent.
-   Id-qualified to outrank that rule. */
-#right-context-rail > #street-level-panel.panel-floating > .street-level-panel-inner {
-  max-height: calc(100vh - 12px);
-  overflow-y: auto;
-}
-
-/* A resized window (inline height) gives its spare height to the viewer. */
-.panel-floating[style*='height'] > .street-level-panel-inner {
-  box-sizing: border-box;
-  height: 100%;
-  max-height: none;
-  overflow: hidden;
-}
-
-.panel-floating[style*='height'] .sl-body,
-.panel-floating[style*='height'] .sl-main {
-  flex: 1 1 auto;
-  min-height: 0;
-}
-
-.panel-floating[style*='height'] .sl-viewer-wrap {
-  flex: 1 1 auto;
-  min-height: 0;
-}
-
-.panel-floating[style*='height'] .sl-viewer-stage {
-  flex: 1 1 auto;
-  min-height: 140px;
-}
-
-.panel-floating[style*='height'] .sl-viewer {
-  flex: 1 1 auto;
-  height: auto;
-  min-height: 0;
-  aspect-ratio: auto;
-}
-
-.panel-floating[style*='height'] .sl-settings {
-  flex: 0 1 auto;
-  overflow-y: auto;
-  scrollbar-width: thin;
-}
-
 /* ── Expanded viewer ─────────────────────────────────────────────────────── */
 /* Re-parented to <body>: the panel's backdrop-filter would contain a fixed
    child. z-index sits above panels (≤139), below the voice pill (150). */