feat: each citation names the code that asks

A profile that reads a libretro core and the original emulator cited both trees alike, and readers could not tell whether the core or the emulator asked for a file. A cited path now opens with source or upstream, the repository its lines are in. Emulator code a port carries is attributed upstream when the original holds the same value on the cited line.

profile_sync --attribute-refs writes the words from where the lines are found and follows a word already written. The site links each citation to that repository's pin, labels it libretro core or upstream emulator, and says on each file card whose code asks for it. A recale keeps the word, and mame_ref_audit reads the tree it names.

scripts/sourceref.py

@@ -16,6 +16,22 @@ _ANNOTATION_RE = re.compile(r"\s*\([^)]*\)?")
 _LOCATED_RE = re.compile(r"^[^\s:]+:\d+(?:-\d+)?$")
 
 
+# A part opening with one of these words says which declared repository its
+# lines are in: `upstream src/bios.c:40` is the original emulator,
+# `source libretro.c:120` the repository the profile names as its source,
+# usually the libretro port. A reader could not tell which code asked for
+# the file when a profile declares both.
+REPO_ROLES = ("source", "upstream")
+
+
+def ref_role(path: str) -> tuple[str, str]:
+    """The role word a cited path opens with, and the path without it."""
+    word, _, rest = path.partition(" ")
+    if word in REPO_ROLES and rest.strip():
+        return word, rest.strip()
+    return "", path
+
+
 @dataclass(frozen=True)
 class RefPart:
     path: str