Add kubernetes dependency to GitHub Actions test workflow

Fix test failure in tests/test_executor.py::TestClusterExecutor::test_submit_k8s_job
by installing the kubernetes extra dependency alongside dev and test dependencies.

The test was failing with "ModuleNotFoundError: No module named 'kubernetes'"
because the GitHub Actions workflow only installed [dev,test] but not [kubernetes].

Now installs: pip install -e ".[dev,test,kubernetes]"

Verified locally: 120/120 tests passing including the Kubernetes test.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: jeremymanning

.github/workflows/tests.yml

@@ -31,7 +31,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install -e ".[dev,test]"
+        pip install -e ".[dev,test,kubernetes]"
 
     - name: Lint with black
       run: |
@@ -70,7 +70,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install -e ".[dev,test]"
+        pip install -e ".[dev,test,kubernetes]"
         
     - name: Run integration tests
       run: |