docs: fix formatting errors in ARModel docstrings

[alphaleporus]

Describe your changes

Summary of the changes:
This PR fixes strict reStructuredText (reST) formatting errors (specifically unexpected unindents and missing blank lines) in the docstrings of ARModel (common_step, plot_examples, and aggregate_and_plot_metrics).

Motivation and context:
As requested by @sadamov in PR #428, this PR isolates the docstring formatting fixes into a single, focused contribution. These formatting errors previously prevented Sphinx and other documentation generators from properly parsing the parameter and return blocks.

Dependencies:
None.

Issue Link

Relates to #61, #69 (Extracted from closed PR #428)

Type of change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📖 Documentation (Addition or improvements to documentation)

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[Seai5]

Hi @alphaleporus!

I just set up the repo locally (uv + editable + pre-commit) and ran a 1-epoch training to look around the code.
The ARModel docstrings look much cleaner now .

Two tiny suggestions if you want to make it even better before merge:

1. In common_step, the :param: lines — maybe add a blank line after each parameter description? (Sphinx sometimes likes extra space there.)
   Example:
   :param x: Input tensor
   (with blank line here)
   :param y: ...

2. Can we add one more Google-style section at the top of ARModel class docstring? Like:
   """Autoregressive model for neural LAM forecasting.

   Attributes:
   ...

   """

Happy to help test it locally with Sphinx if you add conf.py later.

Excited to contribute more docstring cleanups or Sphinx setup next!

Best,
Hrithik

[alphaleporus]

Hi @Seai5, thanks for testing locally and the kind words!
Regarding the suggestions: I want to be careful about scope creep here. Per @sadamov's feedback on my previous PR, I was asked to keep this strictly limited to fixing the specific unexpected unindent formatting errors that were actively breaking the Sphinx build. Expanding the scope to reformat spacing or add new Attributes: sections to the class docstring is a great idea for a broader documentation overhaul, but I want to keep this PR as minimal as possible for the reviewers.
Happy to revisit if a maintainer prefers otherwise!

[sadamov]

@alphaleporus please direct this PR into #252 PR branch or add a review there with your suggestions (since they are minor)

[joeloskarsson]

Agreed, better to add to #252