feat(decky): native-touch controller layout + restructured shortcuts + artwork

Ship a Steam Input controller layout (controller_config/punktfunk.vdf) whose
always-on `ts_n` command enables native touchscreen delivery on the Deck, and
have the backend auto-install it (apply_controller_config: copy to
controller_base/templates + upsert the per-account configset entry, chown to the
user, back up first). This is what makes the Deck touchscreen reach the client
as native touch under gamescope without disabling Steam Input (impossible on the
Deck) — no manual controller setup.

Two shortcuts sharing the "Punktfunk" name (so one config key covers both): a
hidden stateful stream entry and a visible stateless entry that launches straight
into the gamepad UI. Both get full artwork (grid/gridwide/hero/logo/icon,
replaced with exported PNGs). Drop the art-generation script.

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

clients/decky/scripts/package.sh

@@ -26,8 +26,12 @@ 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 "$DEST/bin/punktfunkrun.sh"
-# Steam-shortcut artwork (grid/hero/logo/icon — scripts/gen-steam-art.py, committed).
+# Steam-shortcut artwork (grid/gridwide/hero/logo/icon — committed under assets/).
 cp assets/*.png "$DEST/assets/"
+# The Steam Input controller layout (native touchscreen `ts_n` + gamepad passthrough) the
+# backend installs (apply_controller_config → controller_base/templates + the shortcut config).
+mkdir -p "$DEST/controller_config"
+cp controller_config/punktfunk.vdf "$DEST/controller_config/punktfunk.vdf"
 [ -f decky.pyi ]  && cp decky.pyi  "$DEST/"
 [ -f README.md ]  && cp README.md  "$DEST/"