Fix coverage job JSON parsing error in CI workflow

Use jq to extract coverage percentage instead of outputting entire JSON.
This resolves GitHub Actions output format error caused by multiline JSON.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: knowledgecode

.github/workflows/test.yml

@@ -52,14 +52,14 @@ jobs:
     - name: Read coverage summary
       id: coverage
       run: |
-        echo "summary=$(cat coverage/coverage-summary.json)" >> $GITHUB_OUTPUT
+        echo "pct=$(jq '.total.lines.pct' coverage/coverage-summary.json)" >> $GITHUB_OUTPUT
 
     - name: Generate coverage badge
       uses: emibcn/badge-action@v2.0.3
       with:
         label: 'coverage'
-        status: ${{ fromJson(steps.coverage.outputs.summary).total.lines.pct }}%
-        color: ${{ fromJson(steps.coverage.outputs.summary).total.lines.pct > 80 && 'brightgreen' || fromJson(steps.coverage.outputs.summary).total.lines.pct > 60 && 'yellow' || 'red' }}
+        status: ${{ steps.coverage.outputs.pct }}%
+        color: ${{ steps.coverage.outputs.pct > 80 && 'brightgreen' || steps.coverage.outputs.pct > 60 && 'yellow' || 'red' }}
         path: badges/coverage.svg
         style: flat