feat: aliases support in resolve and db generation

generate_db.py now reads aliases from emulator YAMLs and indexes
them in database.json by_name. resolve_local_file in common.py
tries all alias names when the primary name fails to match.

beetle_psx alt_names renamed to aliases (was not indexed before).
snes9x BS-X.bios, np2kai FONT.ROM/ide.rom/pci.rom fallbacks,
all now formally declared as aliases and indexed.

verify --all and generate_pack --all pass with 0 regressions.

scripts/common.py

@@ -153,6 +153,8 @@ def resolve_local_file(
     md5_raw = file_entry.get("md5", "")
     name = file_entry.get("name", "")
     zipped_file = file_entry.get("zipped_file")
+    aliases = file_entry.get("aliases", [])
+    names_to_try = [name] + [a for a in aliases if a != name]
 
     md5_list = [m.strip().lower() for m in md5_raw.split(",") if m.strip()] if md5_raw else []
     files_db = db.get("files", {})
@@ -180,14 +182,15 @@ def resolve_local_file(
                         if os.path.exists(path):
                             return path, "md5_exact"
 
-    # 3. No MD5 = any file with that name (existence check)
+    # 3. No MD5 = any file with that name or alias (existence check)
     if not md5_list:
         candidates = []
-        for match_sha1 in by_name.get(name, []):
-            if match_sha1 in files_db:
-                path = files_db[match_sha1]["path"]
-                if os.path.exists(path):
-                    candidates.append(path)
+        for try_name in names_to_try:
+            for match_sha1 in by_name.get(try_name, []):
+                if match_sha1 in files_db:
+                    path = files_db[match_sha1]["path"]
+                    if os.path.exists(path) and path not in candidates:
+                        candidates.append(path)
         if candidates:
             if zipped_file:
                 candidates = [p for p in candidates if ".zip" in os.path.basename(p)]
@@ -195,15 +198,18 @@ def resolve_local_file(
             if primary or candidates:
                 return (primary[0] if primary else candidates[0]), "exact"
 
-    # 5. Name fallback with md5_composite + direct MD5 per candidate
+    # 5. Name + alias fallback with md5_composite + direct MD5 per candidate
     md5_set = set(md5_list)
     candidates = []
-    for match_sha1 in by_name.get(name, []):
-        if match_sha1 in files_db:
-            entry = files_db[match_sha1]
-            path = entry["path"]
-            if os.path.exists(path):
-                candidates.append((path, entry.get("md5", "")))
+    seen_paths = set()
+    for try_name in names_to_try:
+        for match_sha1 in by_name.get(try_name, []):
+            if match_sha1 in files_db:
+                entry = files_db[match_sha1]
+                path = entry["path"]
+                if os.path.exists(path) and path not in seen_paths:
+                    seen_paths.add(path)
+                    candidates.append((path, entry.get("md5", "")))
 
     if candidates:
         if zipped_file:

scripts/generate_db.py

@@ -277,6 +277,37 @@ def _collect_all_aliases(files: dict) -> dict:
     except (ImportError, ConnectionError, OSError):
         pass
 
+    # Collect aliases from emulator YAMLs (aliases field on file entries)
+    emulators_dir = Path("emulators")
+    if emulators_dir.is_dir():
+        try:
+            import yaml
+            for emu_file in emulators_dir.glob("*.yml"):
+                try:
+                    with open(emu_file) as f:
+                        emu_config = yaml.safe_load(f) or {}
+                except (yaml.YAMLError, OSError):
+                    continue
+                for file_entry in emu_config.get("files", []):
+                    entry_aliases = file_entry.get("aliases", [])
+                    if not entry_aliases:
+                        continue
+                    entry_name = file_entry.get("name", "")
+                    sha1 = file_entry.get("sha1", "")
+                    md5 = file_entry.get("md5", "")
+                    matched = None
+                    if sha1 and sha1 in files:
+                        matched = sha1
+                    elif md5 and md5 in md5_to_sha1:
+                        matched = md5_to_sha1[md5]
+                    elif entry_name and entry_name in name_to_sha1:
+                        matched = name_to_sha1[entry_name]
+                    if matched:
+                        for alias_name in entry_aliases:
+                            _add_alias(alias_name, matched)
+        except ImportError:
+            pass
+
     # Identical content named differently across platforms/cores
     KNOWN_ALIAS_GROUPS = [
         # ColecoVision - all these are the same 8KB BIOS