Fix CI: install the package before running tests

The workflow ran unittest against a bare checkout, so with the src/ layout
apple_notes_cli was never importable and every run failed with
ModuleNotFoundError. Local runs passed because `uv run` installs the project
automatically, which hid it.

Installs with `pip install -e .` first, and smoke-tests the console script so
the packaging metadata is covered too. Verified in a clean Python 3.10 venv:
48 tests pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.github/workflows/tests.yml

@@ -16,4 +16,7 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
+      # src/ layout: the package must be installed to be importable.
+      - run: python -m pip install -e .
       - run: python -m unittest discover -s tests -v
+      - run: apple-notes --help