feat(ui): portable, resizable rail panels for CCTV

A drag spec can now be `portable`: dragging the panel by its header lifts
it out of the right rail into a fixed window, resizable from all four
edges and corners, that remembers its place and size under the existing
godsEyeView.v8.panelPos.<id> key ({ left, top, width?, height?, floating })
and snaps back on a header double-click. Only CCTV opts in here; the rail
skips .panel-floating panels when measuring and allocating, and its
placement rules in layers.css are guarded so no !important is needed.
PanelPositionControls gains an optional onPanelResized hook, threaded
through PanelChrome to a no-op on the application shell.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

src/ui/panelRails.test.mjs

@@ -59,7 +59,10 @@ function element(
     getBoundingClientRect() {
       return this.rect;
     },
-    matches: (selector) => selector === '[data-panel-id]',
+    matches: (selector) =>
+      selector === '[data-panel-id]' ||
+      (selector === '[data-panel-id]:not(.panel-floating)' &&
+        !classes.has('panel-floating')),
     contains(target) {
       return (
         target === this || this.children.some((child) => child.contains(target))