Server: generate meta.json for builds/ on startup for incremental updates

server/main.py

@@ -151,6 +151,10 @@ async def lifespan(app: FastAPI):
     # Scan launcher versions and generate meta
     logger.info("Scanning launcher versions...")
     
+    # Generate meta.json in builds/ directory
+    logger.info("Generating launcher meta...")
+    generate_launcher_builds_meta()
+    
     # Extract new format ZIPs to versions directory
     logger.info("Extracting new format versions...")
     extract_new_format_versions()
@@ -829,8 +833,79 @@ def calculate_file_hash(file_path: Path) -> str:
     return hash_sha.hexdigest()
 
 
+def generate_launcher_builds_meta():
+    """Generate meta.json in builds/ directory for incremental updates"""
+    import hashlib
+    
+    version = get_current_launcher_version()
+    if not version:
+        return
+    
+    meta_path = BUILDS_DIR / "meta.json"
+    
+    # Check if meta exists and is fresh
+    if meta_path.exists():
+        try:
+            with open(meta_path, 'r', encoding='utf-8') as f:
+                existing = json.load(f)
+                if existing.get("version") == version:
+                    logger.debug("Launcher meta.json already exists and is current")
+                    return
+        except Exception:
+            pass
+    
+    # Generate new meta
+    files = []
+    try:
+        for file_path in BUILDS_DIR.rglob("*"):
+            if file_path.is_file() and file_path.name not in ["meta.json"]:
+                rel_path = str(file_path.relative_to(BUILDS_DIR))
+                stat = file_path.stat()
+                
+                # Calculate hash
+                sha256_hash = hashlib.sha256()
+                with open(file_path, "rb") as f:
+                    for chunk in iter(lambda: f.read(8192), b""):
+                        sha256_hash.update(chunk)
+                
+                files.append({
+                    "path": rel_path,
+                    "size": stat.st_size,
+                    "hash": f"sha256:{sha256_hash.hexdigest()}"
+                })
+    except Exception as e:
+        logger.warning(f"Failed to generate launcher meta: {e}")
+        return
+    
+    meta = {
+        "version": version,
+        "type": "builds",
+        "release_date": datetime.utcnow().isoformat(),
+        "files": files
+    }
+    
+    try:
+        with open(meta_path, 'w', encoding='utf-8') as f:
+            json.dump(meta, f, indent=2)
+        logger.info(f"Generated launcher meta.json with {len(files)} files")
+    except Exception as e:
+        logger.warning(f"Failed to save meta.json: {e}")
+
+
 def scan_launcher_version(version: str) -> Optional[dict]:
     """Scan a launcher version directory and return meta"""
+    # First check if meta exists in builds/ directly (for new format)
+    meta_path = BUILDS_DIR / "meta.json"
+    if meta_path.exists():
+        try:
+            with open(meta_path, 'r', encoding='utf-8') as f:
+                meta = json.load(f)
+                if meta.get("version") == version:
+                    return meta
+        except Exception:
+            pass
+    
+    # Fallback: check versions directory
     version_path = VERSIONS_DIR / version
     
     if not version_path.exists() or not version_path.is_dir():