feat(radio): answer the RTL-SDR card through the radio store

SdrCard calls LocalSdrControls through radio store actions instead of
DOM listeners, and renders its gain options from the receiver's own
R820T gain steps with page-language labels. The display and radio
stores share one owner list (createOwners): the newest connected owner
with an action answers it.

CHANGELOG.md

@@ -58,7 +58,9 @@
   list renders. Street Level's fit and panorama filters and Recent Imagery's
   mode are `UiSegmented` too: the Street Level store's owner answers
   `setPano` and `setRenderMode`, and `RecentImageryReadout` takes
-  `onSetMode`. `syncScopeControls` (`./ui/display`) and
+  `onSetMode`. The local RTL-SDR card's controls call `LocalSdrControls`
+  through the radio store's new `connect`/`act`, and the card labels its gain
+  options itself. `syncScopeControls` (`./ui/display`) and
   `shouldHideCollapsedRightPanels` (`./ui/layout`) are deprecated: the Display
   view and the rail now own what they did. `./ui/input` imports Vue
   (samehkhamis).