Adds support for GPT-5 series of models in `arcade docs`.
Improves error handling when the LLM does not generate a valid JSON for
a given tool sample inputs. Instead of raising an exception, the CLI
uses an empty input, moves on to the next tool, and prints a warning
message asking the user the fill in the input sample manually in
Javascript and Python files.
This PR also moves the Enumerations from a separate `reference.mdx` file
to the main toolkit file, as requested by @EricGustin to simplify the
docs structure.
Renames the `arcade generate-toolkit-docs` command to `arcade docs`. The
`arcade generate-toolkit-docs` command is preserved for backwards
compatibility, but it's now hidden.
Also some minor improvements to CLI help strings and better error
handling. Better error description when the toolkit is not installed
locally (also now mentioning this requirement in the command help).
