fix: pin distribution to trixie (Debian 13 stable)

Debian 13 (trixie) is now stable. Using --distribution testing
causes kernel module mismatch as testing now points to the next
release. Pin to trixie for stability.

Fixes kernel modules error during installation.

💘 Generated with Crush

Assisted-by: GLM-5 via Crush <crush@charm.land>

run.sh

@@ -586,7 +586,7 @@ cd /tmp &&
 rm -rf ./* &&
 echo "Configuring live-build..." &&
 lb config \
-    --distribution testing \
+    --distribution trixie \
     --architectures amd64 \
     --archive-areas "main contrib non-free" \
     --mode debian \