Fix docstring mismatches in the Python bindings

[ayaangazali]

Proposed changes

Four docstring fixes in python/src, all cases where the doc text disagrees with the binding it is attached to. Checked each against the compiled module after rebuilding.

1. dequantize (ops.cpp): the Args: block listed mode last, after global_scale and dtype, but the signature has it before them. Anyone following the doc order positionally gets a TypeError:

wq, s, b = mx.quantize(mx.random.normal((64, 64)), 32, 4)
mx.dequantize(wq, s, b, 32, 4, "affine", None, None)   # signature order, fine
mx.dequantize(wq, s, b, 32, 4, None, None, "affine")   # doc order, TypeError

2. pad (ops.cpp): documented as constant_value, but the keyword is constant_values, so the documented spelling raises TypeError: incompatible function arguments.

3. rfftn (fft.cpp): the Returns: sentence was cut off at "The output" mid-thought. Completed it to match rfft and rfft2 ("The output data type will be complex."), which is also what it returns (complex64).

4. FunctionExporter (export.cpp): fun:\mx.exporter`was missing the leading colon on the role, so it rendered as literal text instead of a link to:func:`mx.exporter``.

Checklist

Put an x in the boxes that apply.

• I have read the CONTRIBUTING document
• I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes
• I have added tests that prove my fix is effective or that my feature works
• I have updated the necessary documentation (if needed)

(docstring text only, no tests; rebuilt CPU-only locally and confirmed the rendered docstrings)

Happy to split this into separate PRs if you would rather review them apart.

---

for transparency: freshman contributor here, and Claude Code helps me scan for this kind of doc/signature drift, but i ran the two TypeError cases above myself, diffed each docstring against its own nb::sig line, and rebuilt to check the strings render before opening this. tell me if any of the rewording should read differently.

[angeloskath]

👍