Move the changelog entry to changelog.d and clear review leftovers

The entry now lives in changelog.d/1471-context-panel-cleanup.md with
credit, as CONTRIBUTING asks, and CHANGELOG.md is back to main.

CURRENT-STATE no longer lists a compact Radio power control and scopes
the readability description to what Cyber keeps. The responsive glow
comment no longer cites the removed Radio popover, and qa-radio's
pick-buffer comment is back above settleRadioFrames.

Four test fixtures stop stubbing the removed launcher sync, and
PanelChrome drops the _syncRailPanelCollapseButton pass-through, wiring
the layout controller straight to _syncPanelCollapseButton.

src/ui/shellLifecycle.test.mjs

@@ -281,7 +281,7 @@ test('weather rail orders between CCTV and Context, observes and syncs chrome',
     const weather = f.nodes.get('weather-panel');
     stack.children = [weather, f.nodes.get('global-context-panel')];
     const synced = [];
-    const chrome = { _syncContextRadioLauncherState() {} };
+    const chrome = {};
     const owner = new PanelLayoutController({
       readHud: () => ({}),
       scheduleCockpitLayout() {},