Add CI test workflow and harden execute() edge cases

- Add .github/workflows/test.yml: runs the pytest suite on push/PR
  across Python 3.10/3.11/3.12. comfy_api is mocked in conftest.py,
  so no ComfyUI install is required.
- execute(): pass a zero-dimension (malformed/empty) input tensor
  through unchanged instead of crashing the resizer.
- execute(): warn when "Prioritize Min Resolution" forces a large
  upscale (>4x) on an extreme aspect ratio, pointing at the strict
  mode as the size-capping alternative.
- Add regression tests for the zero-dim passthrough and the
  extreme-upscale warning.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SqaVwWKNn9bsmmhUkJXhZ2

.github/workflows/test.yml

@@ -0,0 +1,29 @@
+name: Tests
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  pytest:
+    name: pytest (Python ${{ matrix.python-version }})
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.10", "3.11", "3.12"]
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install test dependencies
+        # comfy_api is mocked in conftest.py, so a full ComfyUI install isn't needed.
+        # numpy silences torch's "Failed to initialize NumPy" import warning.
+        run: python -m pip install --upgrade pip pytest torch numpy
+      - name: Run tests
+        run: python -m pytest -q