Make model prefetching automatic in install/run scripts

install-local-gpu.sh and bring-up-local-gpu.sh now call
prefetch-models.sh --sdxl (host-side download, all models including
SDXL/inpaint, ~13GB) automatically rather than treating it as a manual
DNS-troubleshooting step. install-local-gpu.sh drops back to the
invoking user via sudo -u "$SUDO_USER" -H before running it, since
that script itself runs as root and would otherwise leave downloaded
files root-owned. Both call sites are non-fatal: a prefetch failure
logs a warning and the container still starts, falling back to its
own in-container download attempt.

Updated README to match.

install-local-gpu.sh

@@ -170,12 +170,31 @@ else
     echo "  Minimum driver version: 525"
 fi
 
+# ── 6. Prefetch all AI models (host-side, outside Docker) ───────────────────
+# In-container DNS/network is unreliable on some hosts, so downloading on the
+# host up front (including SDXL/inpaint, ~13GB) is the default now rather
+# than a manual troubleshooting step. Best-effort: this script must finish
+# (and leave the GPU/Docker setup done) even if prefetch fails outright.
+# Run as the real invoking user, not root, so downloaded files (and any
+# `pip install --user` side effects) end up owned by that user — this script
+# itself is already running as root via the sudo re-exec above.
+echo ""
+echo "Prefetching AI models (this can take a while for SDXL, ~13GB)..."
+if [ -n "${SUDO_USER:-}" ]; then
+    sudo -u "$SUDO_USER" -H "$REPO_DIR/prefetch-models.sh" --sdxl \
+        || echo "⚠ Model prefetch had failures (see above) — continuing anyway, the container will retry in-container."
+else
+    "$REPO_DIR/prefetch-models.sh" --sdxl \
+        || echo "⚠ Model prefetch had failures (see above) — continuing anyway, the container will retry in-container."
+fi
+
 echo ""
 echo "=================================================="
 echo "  Setup complete."
 echo "  Start the app with:  ./bring-up-local-gpu.sh"
 echo ""
-echo "  If models fail to download inside the container (DNS/firewall"
-echo "  blocked), fetch them on the host first instead:"
-echo "    ./prefetch-models.sh"
+echo "  Models are prefetched automatically by this script and by"
+echo "  bring-up-local-gpu.sh on every start. If any failed above (no"
+echo "  network, etc.), re-run manually any time:"
+echo "    ./prefetch-models.sh --sdxl"
 echo "=================================================="