docs: CCTV panel collapse on switch-off, and changelog fragment

changelog.d/1723-cctv-panel-collapse-on-disable.md

@@ -0,0 +1,4 @@
+- Collapse the CCTV panel when the layer is switched off. It stayed open with
+  an empty frame and a meta line that still described the last camera; the
+  meta line of a disabled layer now reads the catalog count (asturksever,
+  #1723).

docs/CURRENT-STATE.md

@@ -2229,6 +2229,11 @@ shown without a fade once it is decoded (or after one second if its decode never
 settles), so a new camera's preview is blank only while its frame loads. Disposal
 releases listeners, subscriptions, image handlers, summary timers and chip-hide timers.
 
+The panel opens when a camera becomes active and collapses when the layer is
+switched off, from its own switch or anywhere else; a context-mode layer clear
+keeps it as it is. A panel opened by hand while the layer is off stays open,
+and its meta line reads the catalog count, not the last active camera.
+
 ## UI disposal
 
 UI disposal releases the CCTV subscription, command-dock observer, legacy drag