fix: chained reusable workflows

[pablots99]

Problem

When a local workflow calls a reusable workflow from an external repository, and that external workflow calls another reusable workflow from the same external repo using a local reference (./.github/workflows/...), act fails with a "file not found" error.

Local Repo
│
│  uses: org/shared-workflows/.github/workflows/app-ci.yml@main
│
└──► External Repo: app-ci.yml
     │
     │  uses: ./.github/workflows/setup.yml  ← FAILS
     │
     └──► External Repo: setup.yml (not found)

Error: stat /path/to/local/repo/.github/workflows/setup.yml: no such file or directory

The nested workflow reference resolves relative to the local repository instead of the external repository.

Solution

Track the parent workflow's origin through the runner chain. When executing a reusable workflow from an external repo, store a reference to that workflow in the caller struct. When a nested workflow uses a local reference, check if we're inside a remote workflow and resolve the path accordingly.