fix: copy standalone files from their pack path

The registry names one path per standalone copy for every platform,
but each manifest places the file its own way, so the installer
looked where the pack had put nothing and copied nothing: EmuDeck's
aes_keys.txt for Azahar, Batocera's switch/prod.keys. Each manifest
copy now names its source, which the installer validates and reads.

scripts/generate_pack.py

@@ -3226,6 +3226,36 @@ _MANIFEST_HASHES = frozenset({"sha1", "sha256"})
 _STABLE_HASHES: dict[tuple, dict] = {}
 
 
+def _placed_copies(copies: list[dict], dests: list[str]) -> list[dict]:
+    """Each standalone copy with the path this manifest gives its file.
+
+    The registry names one path per file for every platform (one anchor),
+    while each manifest places the file its own way: EmuDeck installs
+    aes_keys.txt at the root and Batocera prod.keys under switch/, so the
+    installer looked for Citra/sysdata/aes_keys.txt, found nothing and
+    copied nothing. `file` stays as written, since it also lays out a custom
+    emulator root; `source` says where the installed file is.
+    """
+    by_name: dict[str, list[str]] = {}
+    for dest in dests:
+        by_name.setdefault(dest.rsplit("/", 1)[-1].casefold(), []).append(dest)
+    placed: list[dict] = []
+    for copy in copies:
+        wanted = copy.get("file")
+        if not wanted or wanted in dests:
+            placed.append(copy)
+            continue
+        tail = [d for d in dests if d.endswith("/" + wanted)]
+        if tail:
+            # The file whose path carries the least on top of the tail.
+            shortest = min(len(d) for d in tail)
+            tail = [d for d in tail if len(d) == shortest]
+        else:
+            tail = by_name.get(wanted.rsplit("/", 1)[-1].casefold(), [])
+        placed.append({**copy, "source": tail[0]} if len(tail) == 1 else copy)
+    return placed
+
+
 def _stable_hashes(local_path: str, db: dict) -> dict:
     """The file's hashes, held against the scan that built the database.
 
@@ -4084,7 +4114,9 @@ def generate_manifest(
         "generated": now,
         "base_destination": base_dest,
         "detect": detect,
-        "standalone_copies": standalone_copies,
+        "standalone_copies": _placed_copies(
+            standalone_copies, [entry["dest"] for entry in manifest_files]
+        ),
         "total_files": len(manifest_files),
         "total_size": total_size,
         "pack_files": (