refactor(download): remove ProviderCore/download.py, move sanitize_filename to SYS.utils, replace callers to use API.HTTP.HTTPClient

SYS/utils.py

@@ -66,6 +66,24 @@ def sanitize_metadata_value(value: Any) -> str | None:
     return value
 
 
+def sanitize_filename(name: str, *, max_len: int = 150) -> str:
+    """Return a filesystem-safe filename derived from *name*.
+
+    Replaces characters that are invalid on Windows with underscores and
+    collapses whitespace. Trims trailing periods and enforces a max length.
+    """
+    text = str(name or "").strip()
+    if not text:
+        return "download"
+
+    forbidden = set('<>:"/\\|?*')
+    cleaned = "".join("_" if c in forbidden else c for c in text)
+    cleaned = " ".join(cleaned.split()).strip().strip(".")
+    if not cleaned:
+        cleaned = "download"
+    return cleaned[:max_len]
+
+
 def unique_preserve_order(values: Iterable[str]) -> list[str]:
     seen: set[str] = set()
     ordered: list[str] = []