Support `.lock.yaml` files

[porada]

Right now, workflow.md gets compiled to workflow.lock.yml. If the file is renamed to workflow.lock.yaml, running gh aw compile creates a new workflow.lock.yml instead of updating the existing workflow.lock.yaml.

Expected Behavior

If workflow.lock.yaml exists, gh aw compile should update it instead of generating workflow.lock.yml.

Rationale

Even though .yml is the default file extension for workflow files, GitHub supports .yaml files in .github/workflows (like here), providing consistency for repositories where .yaml is the established pattern. This includes support for dependabot.yaml and action.yaml in workflow action repositories (living proof).

[pelikhan]

How critical is this?

[porada]

It’s nice to have, but not critical.