ci: Switch from coverage comments to codecov.io (#78)

## Summary

Replaces the current coverage comment system with codecov.io integration
for better coverage tracking and open source best practices.

## Changes

### Removed:
- `irongut/CodeCoverageSummary` action that generates markdown summaries
- `marocchino/sticky-pull-request-comment` action that posts PR comments

### Added:
- `codecov/codecov-action@v4` to upload coverage data to codecov.io
- Configured with `fail_ci_if_error: false` for graceful handling
- Uses existing coverage.xml from pytest

## Benefits

✅ **Professional coverage reporting** with codecov.io dashboard  
✅ **Coverage badges** for README  
✅ **Coverage trend tracking** over time  
✅ **Better open source integration** - standard for OSS projects  
✅ **No more PR comment spam** - cleaner PR experience  
✅ **Free for open source** projects  

## Setup Required

After merging, you'll need to:

1. **Visit [codecov.io](https://codecov.io)** and sign in with GitHub
2. **Enable the batfish/lab-validation repository**
3. **Add coverage badge** to README (optional)

No additional secrets or configuration needed - codecov-action works
automatically for public repos.

## Testing

This PR tests the new codecov integration. The coverage data should be
uploaded to codecov.io when the CI runs.

Author: dhalperi

.github/workflows/ci.yml

@@ -26,6 +26,8 @@ jobs:
 
   test:
     runs-on: ubuntu-latest
+    permissions:
+      id-token: write
 
     steps:
     - uses: actions/checkout@v4
@@ -48,25 +50,14 @@ jobs:
       run: |
         pytest tests/ -v --tb=short --cov=lab_validation --cov-report=xml --cov-report=term-missing
 
-    - name: Code Coverage Summary
-      uses: irongut/CodeCoverageSummary@v1.3.0
+    - name: Upload coverage to Codecov
+      uses: codecov/codecov-action@v5
       with:
-        filename: coverage.xml
-        badge: true
-        fail_below_min: false
-        format: markdown
-        hide_branch_rate: false
-        hide_complexity: true
-        indicators: true
-        output: both
-        thresholds: '60 80'
-
-    - name: Add Coverage PR Comment
-      uses: marocchino/sticky-pull-request-comment@v2
-      if: github.event_name == 'pull_request'
-      with:
-        recreate: true
-        path: code-coverage-results.md
+        files: ./coverage.xml
+        flags: unittests
+        name: codecov-umbrella
+        fail_ci_if_error: false
+        use_oidc: true
 
     - name: Test package build
       run: |