docs(release): add a release note for the zoom shortcuts

The Release note gate requires an added `.changes/*.md` for runtime changes;
the shortcuts are a user-visible feature of their own, so they get their own
note and the persistence note stays about persistence.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.changes/shell-zoom-level-persistence.md

@@ -4,8 +4,6 @@ area: shell
 issues: [1109]
 ---
 
-The app now remembers your zoom level (Cmd/Ctrl and +/-, Cmd/Ctrl+0 to
-reset): it holds when you switch between sections or resize the window, and
-comes back after a restart, so a larger font size no longer resets to the
-default. Windows and Linux gain the zoom shortcuts, which had only worked
-through the macOS menu.
+The app now remembers your zoom level (Cmd/Ctrl and +/-): it holds when you
+switch between sections or resize the window, and comes back after a
+restart, so a larger font size no longer resets to the default.

.changes/shell-zoom-shortcuts.md

@@ -0,0 +1,10 @@
+---
+type: feature
+area: shell
+issues: [1109]
+---
+
+Zoom the app from the keyboard on every platform: Ctrl (Cmd on macOS) with
++/- steps the size in about 10 % increments, including on the numpad, and
+Ctrl/Cmd+0 returns to the default. Windows and Linux gain these shortcuts,
+which previously existed only in the macOS menu.