Feature: Run a Deployment sub-step

Currently, BitOps glues several steps into a single monolithic pipeline.
According to feedback, BitOps should allow a controlled run of a specific sub-step of the deployment.

This will be helpful in debugging, developing, or even trying to re-run the specific step in the middle of the failed pipeline without triggering the entire workflow which is time-consuming.

With the deployment workflow including `terraform`, `helm`, and `ansible`, the tool should be able to provide a CLI endpoint to run only specific step like `ansible`.
Ideas:
```
bitops run ansible <...options>
bitops deploy ansible <...options>
bitops ansible <...options>
```

## TODO
- [ ] Implementation
- [ ] CLI endpoint
- [ ] Testing
- [ ] Documentation

Start by reviewing BitOps' existing CLI entry points and deployment workflow, then compare the proposed `bitops run`, `bitops deploy`, and direct step commands. Done means one selected Terraform, Helm, or Ansible step can run without triggering the full workflow, with coverage for the CLI behavior and documentation for its options.

Written by the indexing model from the issue text.