fix: standardize safety validation (Phase 2 audit remediation)

src/alscan/parser.py

@@ -35,6 +35,11 @@ def parse_als(path: str | Path) -> Project:
     path = Path(path).resolve()
     if not path.exists():
         raise FileNotFoundError(str(path))
+    file_size = path.stat().st_size
+    if file_size == 0:
+        raise ValueError(f"ALS file is empty: {path}")
+    if file_size < 50:
+        raise ValueError(f"ALS file is too small to be valid ({file_size} bytes): {path}")
     raw = path.read_bytes()
     if raw[:2] == b"\x1f\x8b":
         buf = io.BytesIO(raw)

src/alscan/services.py

@@ -316,6 +316,11 @@ def save_report(
     dest: Path,
     source_paths: list[Path] | None = None,
 ) -> Path:
+    """Save a report to dest with safety validation.
+
+    validate_output_dest() includes validate_parent() which checks for
+    symlink/junction traversal in path components.
+    """
     sources = source_paths or []
     try:
         validate_output_dest(dest, sources)