[Feature] Add a new "oumi fetch" command to pull configs via the CLI

[taenin]

Feature request

Create a new CLI command oumi fetch that will download configs from the oumi github repo to a local directory specified by an environment variable.

Any CLI actions using the oumi:// prefix will look for the config in that folder.

Motivation / references

This makes running Oumi much less disruptive. Users could even set the environment variable to a clone of the oumi repo to run the CLI anywhere. Consider the following:

OUMI_DIR=~/.oumi/configs


oumi infer -c oumi://smollm/inference/135m_infer.yaml \
  --generation.max_new_tokens 40 \
  --generation.temperature 0.7 \
  --interactive

Your contribution

This change requires:

• Adding a new CLI entrypoint
• Updating the config loading logic for each CLI entrypoint to check for the oumi:// prefix and resolve it accordingly.