Round out the icon set + rewrite art/icons/README.md honestly.

Added:
  - cac3-128.png (Linux desktop launcher size)
  - cac3-256.png (Debian package icon size)
  - cac3-1024.png (macOS Retina @2x Qt tray icon)

Re-bundled favicon.ico with 16/32/48/96/128/256 sizes inside.

Rewrote art/icons/README.md to:
  - remove references to non-existent SVG sources
  - document the real PNG regeneration recipe
  - be straight about the 16x16 legibility limit
  - leave room for an artist-provided SVG master if/when one exists

art/icons/README.md

@@ -1,65 +1,84 @@
 # CAC3 Icon Set
 
 ## Source
-Generated from `cac3-master-1024.png`, a 1024×1024 transparent-background
-recolored tribute to the classic California commemorative coin design.
+Generated from a 1254×1254 transparent-background PNG master.
 
-## Files at a glance
+The PNG is the canonical source of truth for this set. There is no
+SVG master — the SVG you see, if any, will be one you provide or one
+an artist provides. We do not fabricate vector sources here.
+
+## Regenerating the PNG set
+
+```bash
+SRC=/path/to/your/cac3-master-1254.png
+cd art/icons
+
+for s in 16 32 48 96 128 192 256 512 1024; do
+  convert "$SRC" -resize ${s}x${s} -filter Lanczos cac3-${s}.png
+done
+convert "$SRC" -resize 1500x1500 -filter Lanczos cac3-app-store.png
+
+convert cac3-16.png cac3-32.png cac3-48.png cac3-96.png \
+        cac3-128.png cac3-256.png favicon.ico
+
+convert "$SRC" -resize 180x180 apple-touch-icon.png
+convert "$SRC" -resize 152x152 apple-touch-icon-ipad.png
+convert "$SRC" -resize 432x432 android-foreground.png
+
+# Android background: solid black so the cream disc pops against it.
+convert -size 432x432 xc:'#0a0a0a' android-background.png
+```
+
+Requires ImageMagick 7+. The CAC3 medallion has pale-on-mid contrast
+which can collapse under naive resampling — `-filter Lanczos` keeps
+the cream paper disc legible at small sizes.
+
+## Files
 
 | File | Size | Purpose |
 |---|---|---|
-| `cac3-master-1024.png` | 1024×1024 | Source of truth for all smaller sizes. Replace this if you regenerate the icon set. |
+| `cac3-master-1024.png` | 1024×1024 | Soft-padded smaller version of the 1254 source for sharing without bundling the full-size PNG in repos |
 | `cac3-app-store.png` | 1500×1500 | Apple App Store / Google Play store-listing size |
 | `cac3-512.png` | 512×512 | PWA / modern desktop |
 | `cac3-192.png` | 192×192 | Android / PWA medium |
-| `cac3-96.png` | 96×96 | Linux desktop, taskbar |
+| `cac3-128.png` | 128×128 | Linux desktop launcher |
+| `cac3-96.png` | 96×96 | Linux taskbar |
 | `cac3-48.png` | 48×48 | Toolbar |
 | `cac3-32.png` | 32×32 | Menu |
-| `cac3-16.png` | 16×16 | Status bar / smallest |
-| `favicon.ico` | 16/32/48/96 multi-icon | Browsers (`.ico` bundle) |
+| `cac3-16.png` | 16×16 | Status bar / smallest readable |
+| `favicon.ico` | 16/32/48/96/128/256 multi-icon | Browser address bar bundle |
 | `favicon-16x16.png` | 16×16 | Browser favicon |
 | `favicon-32x32.png` | 32×32 | Browser favicon (HiDPI) |
 | `favicon-48x48.png` | 48×48 | Browser favicon (Windows) |
 | `apple-touch-icon.png` | 180×180 | iOS home screen |
 | `apple-touch-icon-ipad.png` | 152×152 | iPad home screen |
 | `android-foreground.png` | 432×432, transparent | Android adaptive icon foreground layer |
-| `android-background.png` | 432×432 solid `#0a0a0a` | Android adaptive icon background layer (dark) |
+| `android-background.png` | 432×432, solid `#0a0a0a` | Android adaptive icon background (dark) |
 
-## How to regenerate
+## Planned targets in the source tree
 
-If you change the source master, regenerate everything from a single command:
+These will be referenced when the C++ source lands.
 
-```bash
-SRC=cac3-master-1024.png
-for s in 16 32 48 96 192 512 1024; do
-  convert "$SRC" -resize ${s}x${s} cac3-${s}.png
-done
-convert cac3-16.png cac3-32.png cac3-48.png cac3-96.png favicon.ico
-convert "$SRC" -resize 180x180 apple-touch-icon.png
-convert "$SRC" -resize 152x152 apple-touch-icon-ipad.png
-convert "$SRC" -resize 432x432 android-foreground.png
-convert "$SRC" -resize 1500x1500 cac3-app-store.png
-```
-
-(ImageMagick 7+. For IM6 substitute `magick` for `convert`.)
-
-## Planned targets in this codebase
-
-Once the C++ source lands, these files are referenced in:
-
-| Target file (planned) | Which icon |
+| Target (planned) | Maps to |
 |---|---|
 | `src/qt/res/icons/cac3.png` | `cac3-512.png` |
 | `src/qt/res/icons/cac3.ico` | `favicon.ico` |
 | `src/qt/res/icons/cac3@2x.png` | `cac3-1024.png` |
-| `src/qt/res/icons/cac3-testnet.png` | distinct from mainnet |
-| `src/qt/res/splash.png` (the boot splash) | new generative splash once shipped |
+| `src/qt/res/icons/cac3-testnet.png` | distinct from mainnet (not yet generated) |
 | `contrib/debian/cac3d.desktop` | `cac3-256.png` |
-| `contrib/builder/bootstraps/qml/out/assets/` | `cac3-512.png` |
+| `contrib/macosx/Info.plist` | `cac3-512.png` and `cac3-1024.png` |
+
+## Note on small sizes
+
+At 16×16 the cream paper disc and the dark bear silhouette both
+lighten into the gold rim when resampled down. This is a property
+of the original design, not a render artifact. If this set is used
+as a system tray icon for the wallet, the design may benefit from a
+simplified 16×16 variant — bear head only, no wordmark — that an
+artist provides in addition to the full medallion. That variant
+does not exist yet; it will be added here when it does.
 
 ## License
-The icon design is released under **CC0 1.0 Universal** (public domain
-dedication). Anyone may fork, recolor, or remix it for downstream CAC3
-implementations without attribution. The recoloring of the classic
-California commemorative coin design is a tribute, not a claim of
-authorship.
+The medallion design is released under **CC0 1.0 Universal** (public
+domain dedication). Anyone may fork, recolor, or remix it for
+downstream CAC3 implementations without attribution.