Preserve loader behavior while reducing hidden work (#1996)

* fix(app): preserve loader behavior in retained panels

Keep the running footer mounted across panel switches. Inactive loaders stop their animation work, then realign to the original wall-clock phase before they become visible.

* perf(app): remove inactive loader wrapper worklet

* perf(app): pause hidden turn elapsed timers

* perf(app): reduce loader animation work

Keep one wall-clock-aligned clock for visible loaders and detach retained
hidden loaders without unmounting them. Preserve the 950 ms sequence and
reduced-motion behavior.

docs/mobile-panels.md

@@ -85,6 +85,9 @@ definition, no longer eligible to begin.
 - Panels whose gesture wrapper already owns visibility use `RetainedPanelActivity` to provide the
   same active signal without adding another layout root. Persistent animations, timers, polling, and
   shared clocks must subscribe to that signal and stop when their final visible consumer leaves.
+- Synchronized step animations use one wall-clock-aligned source. Register a local shared value only
+  while its retained panel is active so hidden animated styles remain mounted without receiving clock
+  updates. Do not give every instance its own loop or leave hidden styles subscribed to the source.
 - Retention order and render order are separate concerns. LRU metadata may change on every switch;
   keyed retained roots must keep a stable sibling order. Moving large retained roots triggered Fabric
   Differ failures (`addViewAt` / `removeViewAt` view reuse) on Android.