Closes the no-CI gap surfaced in the post-merge retrospective. The org
reusable workflows live under Sea-Haven-Industries and assume SAM/CDK
projects — orchestrator is a personal CLI tool with neither, so this is
a standalone workflow on the same conventions (actions/checkout@v6,
Python 3.12, ruff).
- lint job: ruff check + ruff format --check.
- test-collect job: installs requirements + runs `pytest --collect-only`.
Catches import errors and golden-set test discovery regressions without
needing live ANTHROPIC/COMPOSIO secrets — full pytest stays a local
pre-push responsibility.
Also adds .DS_Store to the local .gitignore (also covered by the user
global gitignore, but belt-and-suspenders).
