fix(packaging): autoload vhci-hcd and open its attach files for the usbip Deck pad

Steam Input only adopts the virtual Steam Deck controller when it arrives as
a real USB device (raw_gadget or usbip/vhci transports); the UHID fallback
has no USB interface and Steam ignores it. On a stock host neither
precondition for usbip held: vhci-hcd isn't loaded, and its sysfs
attach/detach files are root-only while the host runs as a user service —
so every session silently fell back to UHID and 'no controller appears on
the host' (live-debugged 2026-07-08: client events all arrived, the pad
existed, Steam just refused it).

Ship both preconditions with the host packages:
 * modules-load.d/punktfunk.conf loads vhci-hcd at boot (rpm/deb/arch;
   Bazzite gets it via the RPM payload + a modprobe in the sysext
   post-merge hook)
 * a udev rule in 60-punktfunk.rules grants the input group write on
   vhci_hcd's attach/detach whenever the device appears

Verified end-to-end on a live host: usbip in-process attach, hid-steam
binds all three interfaces, 'Steam Deck' + motion evdev appear, and Steam
adopts the pad (client-mode grab + its own virtual X360 emission).

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

packaging/debian/build-deb.sh

@@ -42,6 +42,8 @@ SHAREDIR="$STAGE/usr/share/$PKG"
 # --- file layout (matches the RPM %install) ----------------------------------
 install -Dm0755 "$BIN"                              "$STAGE/usr/bin/$PKG"
 install -Dm0644 scripts/60-punktfunk.rules         "$STAGE/usr/lib/udev/rules.d/60-punktfunk.rules"
+# vhci-hcd autoload — usbip transport for the virtual Steam Deck pad (Steam only adopts USB pads).
+install -Dm0644 scripts/punktfunk-modules.conf     "$STAGE/usr/lib/modules-load.d/punktfunk.conf"
 # UDP socket-buffer tuning (32 MB) — without it the kernel clamps the host's SO_SNDBUF to ~416 KB
 # and high-bitrate frames overflow it (send-side packet loss). systemd-sysctl applies it at boot.
 install -Dm0644 scripts/99-punktfunk-net.conf      "$STAGE/usr/lib/sysctl.d/99-punktfunk-net.conf"