fix: a shared tail is proof only in the own tree

PCSX2x6 reads bin/resources/GameIndex.yaml, an arcade database keyed by NM gameid. The shortened tail resources/GameIndex.yaml matched four files, and the resolver set aside the three in other emulators' trees before measuring ambiguity, so PCSX2's console database passed for path proof and shipped in the PCSX2x6 pack. Ambiguity is now read before that filtering. A tail indexed from an identical copy is kept even when the database records the other copy's path.

PCSX2x6's GameIndex.yaml and RedumpDatabase.yaml are collected from its repository at the pinned 583f0e90 (git blobs ed8232e3 and 8669b3af).

scripts/common.py

@@ -897,6 +897,14 @@ def _foreign_tree(path: str, owners: set[str]) -> bool:
     return not (owners & _affinity_tokens(parts[2]))
 
 
+def _own_tree(path: str, owners: set[str]) -> bool:
+    """Whether a path lives in the bios/Other/<emulator>/ tree of the asker."""
+    parts = path.split("/")
+    if not owners or len(parts) < 4 or parts[0] != "bios" or parts[1] != "Other":
+        return False
+    return bool(owners & _affinity_tokens(parts[2]))
+
+
 def _rank_tail_candidates(
     candidates: list[str], start: int, tail: str, files_db: dict, owners: set[str],
     asker: frozenset[str] = frozenset(),
@@ -921,9 +929,14 @@ def _rank_tail_candidates(
     # pins on every desktop target. A platform's own declaration has no
     # asker, and the tree whose path is its destination still answers it.
     if start or asker:
+        # The database keeps one path per content. When that path does not
+        # end with the tail, the tail was indexed from an identical copy
+        # elsewhere, and the recorded path says nothing about whose tree it
+        # sits in: PCSX2x6's RedumpDatabase.yaml has EmuCoreX's bytes.
         candidates = [
             h for h in candidates
-            if not _foreign_tree(path_of(h), owners if start else set(asker))
+            if not path_of(h).endswith("/" + tail)
+            or not _foreign_tree(path_of(h), owners if start else set(asker))
         ]
     if len(candidates) < 2:
         return candidates
@@ -1304,6 +1317,18 @@ def resolve_local_file(
                 by_path_suffix.get(tail, []), start, tail, files_db, owners,
                 frozenset(_owner_tokens(file_entry)),
             )
+            raw = by_path_suffix.get(tail, [])
+            if start and len(raw) > 1:
+                # Ambiguity is read before the foreign trees are set aside:
+                # PCSX2x6's bin/resources/GameIndex.yaml met four copies
+                # under resources/GameIndex.yaml, three in other emulators'
+                # trees, and the fourth (PCSX2's console database, not
+                # PCSX2x6's arcade one) passed for proof. Only the asker's own
+                # tree still answers a tail several files share.
+                candidates = [
+                    h for h in candidates
+                    if _own_tree(files_db.get(h, {}).get("path", ""), owners)
+                ]
             if start and len(candidates) > 1:
                 continue
             # The index names the file this destination designates. Not on