docs: changelog fragment for the right rail tabs (#1425)

Co-Authored-By: Claude Fable 5.1 <[email protected]>

changelog.d/1425-right-rail-vertical-tabs.md

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+- The right rail (Display, CCTV, Street Level, Context, plus Weather and Recent
+  Imagery while shown) is a vertical tab strip with sideways labels instead of
+  an accordion of collapsed launcher cards: the open panel sits beside the
+  strip and at most one panel is open in every desktop HUD layout. The tabs
+  are a keyboard-navigable tablist, Escape inside a panel returns focus to its
+  tab, and saved preferences and share links are unchanged. Phones keep their
+  sheet shell (gekh, #1425).