feat(decky): visible branded Steam shortcut, one-tap client updates, fullscreen-page polish

- The "Punktfunk" shortcut is no longer hidden: it now ships committed
  artwork (grid/wide/hero/logo/icon, generated by scripts/gen-steam-art.py
  — a pure-stdlib SDF renderer drawing the lens mark + a monoline
  "punktfunk" wordmark) applied via SetCustomArtworkForApp /
  SetShortcutIcon. Existing installs are unhidden and re-arted once per
  ART_VERSION; relaunching the library entry streams to the last host.
- Updates cover the flatpak CLIENT too: check_update compares the
  user-scope installed commit against its remote, applyUpdate runs
  `flatpak update --user` first (awaited) and the plugin reinstall —
  which reloads the panel — last; docs spell out the sudo-less --user
  update ("sudo flatpak update" silently skips per-user installs).
- Fullscreen page: DialogButton stretches to 100% width in the gamepad
  UI, so the Stream/Pair/Refresh/… actions filled whole rows — sized to
  content + right-aligned now; the header drops its Update button (About
  tab + QAM banner keep the flow) and the back button gets a real 40px
  hit target.
- Settings: the disable-Steam-Input note also shows for Automatic — on a
  Deck that now forwards the built-in controller as a Steam Deck pad
  (paddles/trackpads/gyro), which needs Steam Input off for the shortcut.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

clients/decky/scripts/package.sh

@@ -20,12 +20,14 @@ VER="$(python3 -c 'import json;print(json.load(open("package.json"))["version"])
 
 STAGE="$(mktemp -d)"
 DEST="$STAGE/$NAME"
-mkdir -p "$DEST/dist" "$DEST/bin"
+mkdir -p "$DEST/dist" "$DEST/bin" "$DEST/assets"
 cp dist/index.js "$DEST/dist/index.js"          # ship the bundle only, not the sourcemap
 cp main.py plugin.json package.json LICENSE "$DEST/"
 # The stream-launch wrapper (target of the Steam shortcut) — must stay executable.
 cp bin/punktfunkrun.sh "$DEST/bin/punktfunkrun.sh"
 chmod 0755 "$DEST/bin/punktfunkrun.sh"
+# Steam-shortcut artwork (grid/hero/logo/icon — scripts/gen-steam-art.py, committed).
+cp assets/*.png "$DEST/assets/"
 [ -f decky.pyi ]  && cp decky.pyi  "$DEST/"
 [ -f README.md ]  && cp README.md  "$DEST/"