scope pytest to this repository's tests

`dora run` vendors a `git:` node's source into git/ inside the checkout, and
pytest collected that node's tests along with these: running the webcam example
and then the test suite reported 67 tests, 26 of them another project's. A
failure there would have gone red here, for a reason no one would find quickly.

pyproject.toml

@@ -37,6 +37,13 @@ build-backend = "hatchling.build"
 [tool.hatch.build.targets.wheel]
 packages = ["dora_image_view"]
 
+[tool.pytest.ini_options]
+# Only this repository's tests. `dora run` vendors a `git:` node's source into
+# git/ inside the checkout, and pytest would otherwise collect that node's tests
+# too -- reporting another project's results as this one's, and going red when
+# they fail.
+testpaths = ["tests"]
+
 [tool.ruff.lint]
 extend-select = ["D", "I", "N", "RET", "UP"]