ci: match reference repo coverage comment format

Use pytest-xml-coverage-path with coverage-path-prefix so the action
correctly resolves XML paths (relative to subdir) against PR diff paths.
Combined with report-only-changed-files: true, when no source files
are in the diff this shows: badge + Coverage Report dropdown with
TOTAL row + 'No files were changed' note + test summary table.

Matches the format used in Multi-Agent-Custom-Automation-Engine PR #961.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Shreyas-Microsoft

.github/workflows/test.yml

@@ -78,21 +78,6 @@ jobs:
             --junitxml=pytest.xml \
             -v
 
-      - name: Generate coverage summary
-        if: env.skip_backend_tests == 'false'
-        run: |
-          python -c "
-          import xml.etree.ElementTree as ET
-          tree = ET.parse('src/backend-api/reports/coverage.xml')
-          root = tree.getroot()
-          stmts = int(root.attrib.get('lines-valid', 0))
-          miss = stmts - int(root.attrib.get('lines-covered', 0))
-          cover = int(float(root.attrib.get('line-rate', 0)) * 100)
-          with open('src/backend-api/reports/coverage-summary.txt', 'w') as f:
-              f.write('Name     Stmts   Miss  Cover\n')
-              f.write(f'TOTAL    {stmts}    {miss}    {cover}%\n')
-          "
-
       - name: Pytest Coverage Comment
         if: |
           always() &&
@@ -101,8 +86,10 @@ jobs:
           env.skip_backend_tests == 'false'
         uses: MishaKav/pytest-coverage-comment@26f986d2599c288bb62f623d29c2da98609e9cd4  # v1.6.0
         with:
-          pytest-coverage-path: src/backend-api/reports/coverage-summary.txt
+          pytest-xml-coverage-path: src/backend-api/reports/coverage.xml
           junitxml-path: src/backend-api/pytest.xml
+          coverage-path-prefix: src/backend-api/
+          report-only-changed-files: true
 
       - name: Skip Backend Tests
         if: env.skip_backend_tests == 'true'
@@ -150,21 +137,6 @@ jobs:
             --junitxml=pytest.xml \
             -v
 
-      - name: Generate coverage summary
-        if: env.skip_processor_tests == 'false'
-        run: |
-          python -c "
-          import xml.etree.ElementTree as ET
-          tree = ET.parse('src/processor/reports/coverage.xml')
-          root = tree.getroot()
-          stmts = int(root.attrib.get('lines-valid', 0))
-          miss = stmts - int(root.attrib.get('lines-covered', 0))
-          cover = int(float(root.attrib.get('line-rate', 0)) * 100)
-          with open('src/processor/reports/coverage-summary.txt', 'w') as f:
-              f.write('Name     Stmts   Miss  Cover\n')
-              f.write(f'TOTAL    {stmts}    {miss}    {cover}%\n')
-          "
-
       - name: Pytest Coverage Comment (Processor)
         if: |
           always() &&
@@ -173,10 +145,12 @@ jobs:
           env.skip_processor_tests == 'false'
         uses: MishaKav/pytest-coverage-comment@26f986d2599c288bb62f623d29c2da98609e9cd4  # v1.6.0
         with:
-          pytest-coverage-path: src/processor/reports/coverage-summary.txt
+          pytest-xml-coverage-path: src/processor/reports/coverage.xml
           junitxml-path: src/processor/pytest.xml
+          coverage-path-prefix: src/processor/
           title: Processor Coverage Report
           unique-id-for-comment: processor
+          report-only-changed-files: true
 
       - name: Skip Processor Tests
         if: env.skip_processor_tests == 'true'