build(learn): the F-Droid repository keeps the kingfisher as its icon

The repository is all of Halkyon's apps', so its icon stays Halkyon's
emblem (ADR 0031, D3), kept in tool/release/fdroid/ now that the snap's
icon is Learn's graduation cap. Learn's listing keeps the snap's.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

docs/adr/0031-the-apps-icons.md

@@ -42,7 +42,8 @@ through a colour between them (violet or sky) stays bright.
   the palette's (`#273EB2`); violet is no palette colour (between cobalt and strawberry);
   the others are halkyon_ui's palette's.
 - **D3 Learn's icon becomes the graduation cap; the kingfisher stays Halkyon's emblem**,
-  in the logo and the wordmark. Installed Learn apps change their icon once, when the new
+  in the logo and the wordmark, and as the icon of the F-Droid repository, which is all of
+  Halkyon's apps' (the developer's, 28 Oct: `tool/release/fdroid/halkyon.png`). Installed Learn apps change their icon once, when the new
   one is built, as do F-Droid's listing and the snap's.
 - **D4 Meditate's glyph is `circle-dot`** (the developer's, over `flower-2`, recommended,
   `wind`, `sprout`, `leaf` and `flower`): a point to rest the eyes on.