feat(icons): shrink the Android adaptive mark 25%, give old square launchers the full-bleed master

The adaptive foreground's asterisk grazed the round mask's safe zone. Scale the
foreground mark 0.75 about the icon centre (25% smaller, the letter-to-star
arrangement unchanged) so it sits well inside the 61% safe zone. Independently,
the legacy square ic_launcher.png now renders the full-bleed master instead of
the safe-zone composite, so old Android (< API 26) shows a large mark rather
than a shrunk one; the legacy round icon keeps the safe-zone composite (a round
mask would clip the master's corner star). Regenerate the layer set, Android
res and the brandbook foreground previews; update ICON_BRANDBOOK.md / ICONS.md.

docs/ICON_BRANDBOOK.md

@@ -123,12 +123,13 @@ So Android is **not** the full-bleed master — it is built as two layers:
   and square** (no rounded corners; the OS supplies the shape). It fills the whole 108 dp
   layer, so the sacrificial outer ring is just more wood.
 - **Foreground** — **only the «Э» + ✻**, transparent, **re-placed** to sit safely inside
-  the mask:
-  - «Э»: box height **53.9 %**, box center **52.3 % / 49.5 %**.
-  - ✻: outer diameter **13.2 %** (smaller than the master's), center **76.3 % / 72.7 %**,
+  the mask. The whole mark is the master's optical placement (nudged right 8 % / down 3 %)
+  scaled **0.75 about the icon centre** — **25 % smaller**, its «Э» ↔ ✻ arrangement
+  unchanged — so the ✻ that used to graze the round mask now sits well inside the **61 %
+  safe zone** with margin to spare:
+  - «Э»: box height **40.4 %**, box center **51.8 % / 49.6 %**.
+  - ✻: outer diameter **9.9 %** (smaller than the master's), center **69.7 % / 67.0 %**,
     tucked closer to the letter.
-  - The mark is centred, then nudged **right 8 % / down 3 %** so it reads optically
-    centred under the round mask, and the whole group fits within the **61 % safe zone**.
 
 Everything else (palette, grain, gradients, star construction) is identical to the master.