Make _http_exists send the ranged GET its docstring describes

[arpitjain099]

The docstring states the requirement exactly, and the body does the one thing it rules out:

def _http_exists(url: str) -> bool:
    """
    Lightweight existence check using a ranged GET so CDNs/servers that ignore HEAD still work.
    """
    try:
        resp = make_head_request(url, headers={"Range": "bytes=0-0"})

make_head_request is requests.head. Two things follow. The Range header is meaningless on a HEAD, so the 206 this function tests for is never observed on that path; and requests.head defaults to allow_redirects=False, so a 302 also reads as "missing".

The combination takes out the HuggingFace lane. huggingface.py accepts exactly one extension, ALLOWED_EXECUTABLE_EXTS = (".bin",), every real .bin weight file on HuggingFace is Git-LFS backed, and HF serves those from a CDN behind a 302. So the one file class the handler will return is exactly the class this check rejects.

Against a local server with three routes, positive control first so a later failure is not ambiguous:

                                          before    after
plain 200 on HEAD (positive control)      True      True
server answers 405 to HEAD, 200 to GET    False     True
server 302-redirects to a real file       False     True
genuinely missing (negative control)      False     False

The last row matters as much as the middle two: the fix does not simply make everything return True.

Confirmed against the live API too, where a non-LFS file (config.json) already returned True and the LFS weights (model.safetensors, pytorch_model.bin) returned False while a ranged GET on the same URLs answered 206.

The change uses requests.get with the range, redirects followed, and stream=True so the body is not pulled down, closing the response rather than leaving it open. I left make_head_request alone since other callers may want a genuine HEAD.

Note on testing: I could not run the suite here, pytest tests/ fails collection with ModuleNotFoundError: No module named 'pip' in the vendored fetchcode.vcs.pip tests, before and after the change alike, so it is unrelated to this. The verification above is a standalone script driving the real _http_exists.