wolf: persist Steam shader cache across sessions

Mount GAME_STORAGE_DIR/steam-cache → /home/retro/.cache so DXVK/Mesa
Vulkan shader compilations survive container restarts. Without this the
cache lived in the ephemeral session home and was wiped on every Wolf
restart, forcing a full recompile each session.

Also create steam-cache/ in initial setup and update-storage so the
directory exists with correct uid-1000 ownership before the container
first starts.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01D8ckUJQtj1pH8jtAddBDZs

services/wolf.sh

@@ -699,7 +699,8 @@ UDEV
     mkdir -p "$GAME_STORAGE_DIR/saves" \
              "$GAME_STORAGE_DIR/media" "$GAME_STORAGE_DIR/lutris" \
              "$GAME_STORAGE_DIR/firefox" "$GAME_STORAGE_DIR/minecraft" \
-             "$GAME_STORAGE_DIR/kodi" "$GAME_STORAGE_DIR/emulators"
+             "$GAME_STORAGE_DIR/kodi" "$GAME_STORAGE_DIR/emulators" \
+             "$GAME_STORAGE_DIR/steam-cache"
 
     # ── Wolf state folder on the game drive ───────────────────────────────────
     # This is the clean way to keep Steam (and everything else) off the OS
@@ -1027,6 +1028,10 @@ case "$1" in
             echo "GAME_STORAGE_DIR=${GAME_DIR}" >> "$SCRIPT_DIR/.env"
         fi
 
+        # Ensure steam-cache dir exists (persists DXVK/Mesa shader cache across sessions)
+        mkdir -p "$GAME_DIR/steam-cache"
+        sudo chown -R 1000:1000 "$GAME_DIR/steam-cache" 2>/dev/null || true
+
         if [ ! -f "$WOLF_CFG" ]; then
             echo "Wolf config not found at $WOLF_CFG — is Wolf running?"
             exit 1
@@ -1795,7 +1800,8 @@ CATALOG = {
         name='WolfSteam', title='Steam',
         icon='https://games-on-whales.github.io/wildlife/apps/steam/assets/icon.png',
         image='ghcr.io/games-on-whales/steam:edge',
-        mounts=['/etc/localtime:/etc/localtime:ro', '/etc/timezone:/etc/timezone:ro'],
+        mounts=['/etc/localtime:/etc/localtime:ro', '/etc/timezone:/etc/timezone:ro',
+                f'{games}/steam-cache:/home/retro/.cache:rw'],
         env=['PROTON_LOG=1', 'RUN_SWAY=true',
              'GOW_REQUIRED_DEVICES=/dev/input/* /dev/dri/* /dev/nvidia*'],
         cap_add=['SYS_ADMIN', 'SYS_NICE', 'SYS_PTRACE', 'NET_RAW', 'MKNOD', 'NET_ADMIN'],