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.

changelog.d/1471-context-panel-cleanup.md

@@ -0,0 +1,7 @@
+- Remove the Radio icon from the Context panel header, along with the compact
+  Radio player it opened; Radio stays in Context as its own section, and
+  Cockpit's compact Radio is unchanged. Context is also easier to read: the
+  Contacts / Space Missions modes are one segmented control, labels and
+  guidance are larger and higher contrast, the standby hint is plain text
+  instead of a dashed box, and the panel draws no glow halo. Cyber keeps its
+  own framed buttons and red titles (asturksever, #1471).