feat: add codecov integration with test results upload

- Add .codecov.yml configuration with project and patch coverage checks (0.05% threshold)
- Configure jest to output test results in JUnit XML format using jest-junit reporter
- Update pytest to output coverage in XML format and test results in JUnit XML format
- Add codecov/codecov-action@v5 step to upload coverage from both jest (lcov) and pytest (xml)
- Add codecov/test-results-action@v1 step to upload test results from both test suites
- Set fail_ci_if_error: false for coverage upload to prevent blocking CI if codecov has issues
- Use if: '!cancelled()' for test results upload to ensure results are uploaded even if tests fail

Follows the same codecov configuration pattern as deepnote-internal and deepnote-toolkit repos.

Note: CODECOV_TOKEN secret needs to be configured in repository settings for codecov uploads to work.

Author: devin-ai-integration[bot]

.codecov.yml

@@ -0,0 +1,10 @@
+coverage:
+  status:
+    project:
+      default:
+        target: auto
+        threshold: 0.05%
+    patch:
+      default:
+        target: auto
+        threshold: 0.05%

.github/workflows/build.yml

@@ -44,7 +44,7 @@ jobs:
           set -eux
           python -m pip install .[test]
 
-          pytest -vv -r ap --cov jupyterlab_deepnote
+          pytest -vv -r ap --cov jupyterlab_deepnote --cov-report=xml --junit-xml=coverage/pytest-results.xml
           jupyter server extension list
           jupyter server extension list 2>&1 | grep -ie "jupyterlab_deepnote.*OK"
 
@@ -54,6 +54,20 @@ jobs:
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
 
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          files: ./coverage.xml,./coverage/lcov.info
+          fail_ci_if_error: false
+
+      - name: Upload test results to Codecov
+        if: '!cancelled()'
+        uses: codecov/test-results-action@v1
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          files: coverage/pytest-results.xml,coverage/junit.xml
+
       - name: Package the extension
         run: |
           set -eux

jest.config.js

@@ -23,6 +23,7 @@ module.exports = {
     '!src/**/.ipynb_checkpoints/*'
   ],
   coverageReporters: ['lcov', 'text'],
+  reporters: ['default', 'jest-junit'],
   testRegex: 'src/.*/.*.spec.ts[x]?$',
   transformIgnorePatterns: [`/node_modules/(?!${esModules}).+`]
 };