Add CI workflow and ignore .DS_Store

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).

.github/workflows/ci.yaml

@@ -0,0 +1,50 @@
+name: CI
+
+on:
+  pull_request:
+    branches: [main]
+  push:
+    branches: [main]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install ruff
+        run: pip install ruff
+
+      - name: Ruff check
+        run: ruff check .
+
+      - name: Ruff format check
+        run: ruff format --check .
+
+  test-collect:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+          cache: pip
+          cache-dependency-path: requirements.txt
+
+      - name: Install dependencies
+        run: |
+          pip install -r requirements.txt
+          pip install pytest python-dotenv
+
+      - name: Pytest collect-only
+        # Verifies all test modules + their imports resolve cleanly.
+        # Live test execution requires ANTHROPIC_API_KEY + COMPOSIO_API_KEY
+        # and runs locally before push, not in CI.
+        run: pytest --collect-only -q

.gitignore

@@ -6,3 +6,4 @@ __pycache__/
 .cache/
 .pytest_cache/
 .ruff_cache/
+.DS_Store