Fix incorrect examples and outputs in the usage docs

[ayaangazali]

Proposed changes

A few things in the usage docs do not match what the code actually does. I ran every example below on current main to check.

compile.rst

• The implicit-state example mixes 3 and 4 space indentation, so copying it into a file gives IndentationError: unexpected indent. Aligned the trailing lines with the rest of the block.
• Typo: "Firt call compiles the function".

indexing.rst

• The arr[:, :, 0] block had a stray array(3, dtype=int32) line that does not belong to either expression, and both outputs were missing their closing paren. Actual result for both is array([[0, 2], [4, 6]], dtype=int32).
• arr.shape was shown as [8] and arr[None].shape as [1, 8]. shape is a tuple, so these print as (8,) and (1, 8).
• The two boolean-mask assignment examples showed array([5.0, 2.0, 6.0], ...) and array([[1.0, 0.0, 1.0], ...]), but MLX drops the trailing .0 for whole valued floats, so they print as array([5, 2, 6], dtype=float32) and array([[1, 0, 1], [0, 0, 1]], dtype=float32).

quick_start.rst

• Same shape issue: a.shape shown as [4], actually (4,).

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)

(docs only; every example above was executed against current main and the new outputs are copied from the actual results)

---

small note on how i work: i'm a freshman contributor and i use Claude Code to help me spot this kind of drift, but for this one i pulled each code block out into a scratch file, ran it, and pasted back what it really printed. if any of these outputs look different on your machine i would like to know, since that would be more interesting than the typo.

[angeloskath]

Thanks!