tests: fix the comfyui Containerfile test instead of living with it red

This test failed on a clean tree for many sessions, and the working belief
became "test 73 is a known failure, ignore it" — which is exactly what a
permanently red suite teaches. The cause was a selector bug: `find
dankclaw -name 'Containerfile*' | head -1` returned whichever Containerfile the
directory listing happened to put first (dankclaw/alloy/Containerfile), so the
assertion read a file that never claimed to be ComfyUI's. It would equally have
passed on a wrong file.

The test now resolves the Containerfile the way the build does — build.context
joined with build.dockerfile, both read from dankclaw/compose.yaml — so it
checks the file the deploy actually builds (dankclaw/Containerfile.comfyui, the
one compose, deploy-remote.sh and the ComfyUI doc all name) and follows a future
rename instead of guessing.

Suite: ALL TESTS PASSED (310), no exceptions to explain away.

tests/comfyui_rocm.bats

@@ -34,9 +34,26 @@ PYEOF
 }
 
 @test "comfyui Containerfile is based on the gfx1151 torch image" {
+    # Resolve the Containerfile the way the build does — build.context joined
+    # with build.dockerfile — rather than asking the filesystem. A
+    # `find … | head -1` here returned whichever Containerfile the directory
+    # listing happened to put first (dankclaw/alloy/Containerfile), so the test
+    # failed for sessions while the real ComfyUI Containerfile was correct — and
+    # it would equally have passed on a wrong file.
     local cf
-    cf=$(find "$REPO_ROOT/dankclaw" -name 'Containerfile*' 2>/dev/null | head -1)
-    [ -n "$cf" ] || { echo "no Containerfile under dankclaw/"; return 1; }
+    cf=$(python3 - "$REPO_ROOT/dankclaw/compose.yaml" "$REPO_ROOT/dankclaw" <<'PYEOF'
+import os, sys, yaml
+with open(sys.argv[1]) as fh:
+    svc = yaml.safe_load(fh)["services"]["comfyui"]
+build = svc.get("build") or {}
+# Compose resolves dockerfile relative to context, context relative to the
+# compose file's own directory.
+print(os.path.normpath(os.path.join(
+    sys.argv[2], build.get("context", "."), build.get("dockerfile", "Containerfile"))))
+PYEOF
+)
+    [ -n "$cf" ] || { echo "could not resolve the comfyui Containerfile"; return 1; }
+    [ -f "$cf" ] || { echo "$cf (from compose build) does not exist"; return 1; }
     grep -q "gfx1151" "$cf" || { echo "$cf does not reference gfx1151"; return 1; }
     grep -q "FROM" "$cf" || { echo "$cf has no FROM"; return 1; }
 }