Add detect-private-key (pre-commit-hooks) and detect-secrets (Yelp) to
catch leaked keys, tokens, and high-entropy strings before they hit the repo.

…etitem__

When __getitem__ is replaced on a C extension type with a Python function,
CPython sets the sq_item slot in tp_as_sequence. This makes
PySequence_Check(tensor) return True (was False in clean PyTorch), causing
torch.tensor([0-d_tensor, ...]) to iterate elements as sequences and call
len() -- which raises TypeError for 0-d tensors. The slot is never cleared
by restoring the original wrapper_descriptor or by delattr.

Fix: null sq_item via ctypes after every decoration/undecoration cycle
(decorate_all_once, unwrap_torch, wrap_torch). Safe because tensor indexing
uses mp_subscript (mapping protocol), not sq_item (sequence protocol).
Verified via tp_name guard; fails silently on non-CPython.

Adds 9 regression tests covering all lifecycle paths.

…nce-slot