Add basic API docs

[svekars]

• The docs build workflow now installs torchmonarch instead of a custom monarch wheel, and sets up library and CUDA paths to ensure all dependencies (especially native ones) are available.
• The ForgeActor class now includes detailed docstrings for its resource attributes (procs, hosts, with_gpus, num_replicas, mesh_name), and the options method provides example usage in the docstring. This makes it easier for users to understand resource configuration for distributed training.
• Adds a docsting for the Service.stop method
• Docstrings from Service methods are copied to ServiceActor methods, ensuring complete documentation for Sphinx autodoc.
• Sphinx configuration changes improve navigation depth

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
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Additional details and impacted files

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  Coverage        ?   63.32%           
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  Files           ?       78           
  Lines           ?     7716           
  Branches        ?        0           
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  Hits            ?     4886           
  Misses          ?     2830           
  Partials        ?        0           

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