Fix IndexError in alignment.py when token id == vocab size (clamp upper bound)

[uduntuntu]

Reproduction on Finnish with alignment showed IndexError: index X is out of bounds for dimension 0 with size V.

Cause: only lower bound was clamped (min=0), so token==V indexed out of range.

Fix: clamp tokens to [0, V-1] and assert valid blank_id/non-empty emissions.

Included minimal repro script and observed OK results after patch.

# Run (in virtualenv):  python test_alignment_out_of_bounds.py
import torch
from whisperx import alignment as A

def run_case(V, tokens, blank_id=0, label=""):
    fe = torch.randn(V, dtype=torch.float32)
    t = torch.tensor(tokens, dtype=torch.long)
    try:
        out = A.get_wildcard_emission(fe, t, blank_id)
        ok = bool(torch.isfinite(out).all())
        print(f"[OK ] {label:40s} -> out.shape={tuple(out.shape)} finite={ok}")
    except Exception as e:
        print(f"[ERR] {label:40s} -> {type(e).__name__}: {e}")

print("Testing whisperx.alignment.get_wildcard_emission")
print("Function:", A.get_wildcard_emission.__code__.co_filename)

# OFF-BY-ONE repro: token == vocab size (V)
run_case(34, [34], 0, "off-by-one (V=34, token=V)")

# Mixed case: wildcard + valid + token==V
run_case(34, [-1, 0, 5, 34], 0, "wildcard + in-range + token=V")

# Edge case: empty emissions (should assert / error, but not IndexError from indexing)
run_case(0, [0], 0, "empty emissions (V=0)")