v2: automated BIOS platform with full pipeline

Reorganized 6 branches into bios/Manufacturer/Console/.
Scrapers for RetroArch, Batocera, Recalbox, and libretro core-info.
Platform-aware verification replicating native logic per platform.
Pack generation with dedup, alias resolution, variant support.
CI/CD: weekly auto-scrape, auto-release, PR validation.
Large files (>50MB) stored as GitHub Release assets, auto-fetched at build time.

scripts/common.py

@@ -0,0 +1,102 @@
+"""Shared utilities for retrobios scripts.
+
+Single source of truth for platform config loading, hash computation,
+and file resolution - eliminates DRY violations across scripts.
+"""
+
+from __future__ import annotations
+
+import hashlib
+import os
+import zipfile
+import zlib
+from pathlib import Path
+
+try:
+    import yaml
+except ImportError:
+    yaml = None
+
+
+def compute_hashes(filepath: str | Path) -> dict[str, str]:
+    """Compute SHA1, MD5, SHA256, CRC32 for a file."""
+    sha1 = hashlib.sha1()
+    md5 = hashlib.md5()
+    sha256 = hashlib.sha256()
+    crc = 0
+    with open(filepath, "rb") as f:
+        for chunk in iter(lambda: f.read(65536), b""):
+            sha1.update(chunk)
+            md5.update(chunk)
+            sha256.update(chunk)
+            crc = zlib.crc32(chunk, crc)
+    return {
+        "sha1": sha1.hexdigest(),
+        "md5": md5.hexdigest(),
+        "sha256": sha256.hexdigest(),
+        "crc32": format(crc & 0xFFFFFFFF, "08x"),
+    }
+
+
+def md5sum(filepath: str | Path) -> str:
+    """Compute MD5 of a file - matches Batocera's md5sum()."""
+    h = hashlib.md5()
+    with open(filepath, "rb") as f:
+        for chunk in iter(lambda: f.read(65536), b""):
+            h.update(chunk)
+    return h.hexdigest()
+
+
+def load_platform_config(platform_name: str, platforms_dir: str = "platforms") -> dict:
+    """Load a platform config with inheritance and shared group resolution.
+
+    This is the SINGLE implementation used by generate_pack, generate_readme,
+    verify, and auto_fetch. No other copy should exist.
+    """
+    if yaml is None:
+        raise ImportError("PyYAML required: pip install pyyaml")
+
+    config_file = os.path.join(platforms_dir, f"{platform_name}.yml")
+    if not os.path.exists(config_file):
+        raise FileNotFoundError(f"Platform config not found: {config_file}")
+
+    with open(config_file) as f:
+        config = yaml.safe_load(f) or {}
+
+    # Resolve inheritance
+    if "inherits" in config:
+        parent = load_platform_config(config["inherits"], platforms_dir)
+        merged = {**parent}
+        merged.update({k: v for k, v in config.items() if k not in ("inherits", "overrides")})
+        if "overrides" in config and "systems" in config["overrides"]:
+            merged.setdefault("systems", {})
+            for sys_id, override in config["overrides"]["systems"].items():
+                if sys_id in merged["systems"]:
+                    merged["systems"][sys_id] = {**merged["systems"][sys_id], **override}
+                else:
+                    merged["systems"][sys_id] = override
+        config = merged
+
+    # Resolve shared group includes
+    shared_path = os.path.join(platforms_dir, "_shared.yml")
+    if os.path.exists(shared_path):
+        with open(shared_path) as f:
+            shared = yaml.safe_load(f) or {}
+        shared_groups = shared.get("shared_groups", {})
+        for system in config.get("systems", {}).values():
+            for group_name in system.get("includes", []):
+                if group_name in shared_groups:
+                    system.setdefault("files", []).extend(shared_groups[group_name])
+
+    return config
+
+
+def safe_extract_zip(zip_path: str, dest_dir: str) -> None:
+    """Extract a ZIP file safely, preventing zip-slip path traversal."""
+    dest = os.path.realpath(dest_dir)
+    with zipfile.ZipFile(zip_path, "r") as zf:
+        for member in zf.infolist():
+            member_path = os.path.realpath(os.path.join(dest, member.filename))
+            if not member_path.startswith(dest + os.sep) and member_path != dest:
+                raise ValueError(f"Zip slip detected: {member.filename}")
+            zf.extract(member, dest)