feat: run content checks profiles declare

validation: [romdir] walks a PS2 ROM directory the way the profile's
fork reads it, masked_sha1 hashes a file with a byte range cleared, and
size_multiple bounds a size to a granule. The resolver name steps, the
pack and manifest scans, the emulator expansion and verify call the same
content_fits. A PCSX2 companion is taken only beside an image that
passes, and a companion placeholder no longer seeds a scan of its own.

scripts/validate_schemas.py

@@ -95,7 +95,9 @@ _CHECK_FIELDS = {
     "md5": ("md5",),
     "sha1": ("sha1",),
     "sha256": ("sha256",),
-    "size": ("size", "min_size", "max_size"),
+    "size": ("size", "min_size", "max_size", "size_multiple"),
+    "romdir": ("romdir",),
+    "masked_sha1": ("masked_sha1",),
 }