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/CURRENT-STATE.md

@@ -2978,11 +2978,8 @@ and is refused in the cockpit: turning FOLLOW on claims the camera at once, and
 FOLLOW stops when another feature takes it; a photo takes a deferred ticket
 when it starts opening and frames only if nothing newer took the camera while
 it loaded. SINCE is a stepped slider whose readout names the
-cut-off date. The panel is portable (`street-level-panel` spec, minimum
-320 × 280, `dockOnCollapse`): a floating window gives spare height to the
-viewer, and collapsing it, double-clicking the header or SHRINK after EXPAND
-docks it. At phone width (≤720 px) the viewer height is derived from the rail
-band so the whole photo fits.
+cut-off date. At phone width (≤720 px) the viewer height is derived from the
+rail band so the whole photo fits.
 
 Providers implement the contract in `src/layers/streetLevel/registry.js`. The
 core routes clicks by pick prefix, swaps viewer adapters in the one host,
@@ -2998,8 +2995,8 @@ runs against real Mapillary and needs `MAPILLARY_CLIENT_TOKEN`. `npm run
 qa:street-level:fixtures -- --url <server>` answers every Mapillary request
 from fixtures (`providers/mapillary/coverageFixture.mjs`,
 `scripts/fixtures/street-level/`), so it needs no network and covers the whole
-photo flow. CI runs the fixture gate and `qa:panel-resize`
-against a production build served by `vite preview` with a dummy token.
+photo flow. CI runs the fixture gate against a production build served by
+`vite preview` with a dummy token.
 
 Directions is a keyless front end to the routing the voice agent already
 uses. Its row chips are the whole interface: DRIVE / WALK / BIKE pick the
@@ -4429,8 +4426,8 @@ easier to meet (detection is now on more often), but does not create it.
   samples and constant elevation during E/N drag; one shared-floor resolution on
   release; late one-shot shared-cell work is permitted during viewshed idle. The
   A+B harness intentionally excludes citywide LOD assertions.
-- Panel positions have a versioned storage name, `godsEyeView.v8.panelPos.<panel-id>`. Docked panels store nothing; a portable panel (CCTV, Street Level) stores `{ left, top, width, height, floating: true }` once a header drag lifts it out of the rail, and a header double-click removes it. Double presses are detected in the header's `pointerdown` handler, because its `preventDefault()` suppresses native `dblclick`. Collapsed state persists for every panel at `godsEyeView.v6.panelCollapsed.<panel-id>` (`'0'` open, `'1'` closed, absent means the panel's own default).
-- Legacy draggable-panel position keys may remain in local storage for backward compatibility, but the map-mode right rail ignores them unless they describe a portable panel's floating window; collapsed states still persist at `godsEyeView.v6.panelCollapsed.<panel-id>`.
+- Panel positions have a versioned storage name, `godsEyeView.v8.panelPos.<panel-id>`, but the current rails lay panels out adaptively and write none. Collapsed state does persist for every panel at `godsEyeView.v6.panelCollapsed.<panel-id>` (`'0'` open, `'1'` closed, absent means the panel's own default).
+- Legacy draggable-panel position keys may remain in local storage for backward compatibility, but the map-mode right rail ignores them; collapsed states still persist at `godsEyeView.v6.panelCollapsed.<panel-id>`.
 - Flight/military tracked entities cache dead-reckoned positions per frame to avoid callback desync flicker.
 - Aircraft 3D-model and tracking invariants are covered by `npm run test:track`; run this before touching `flights.js`, `militaryFlights.js`, `detection.js`, or `trackedReadout.js`.
 - Annotation resolver behavior is pinned by `src/annotations/annotationResolver.test.mjs`; re-run that suite before changing place-resolution scoring.