refactor: simplify performance workflow to reliable baseline

WHAT WORKS:
- Run benchmark twice: once for human-readable output, once for JSON
- Save JSON as artifact for maintainer review
- No fragile shell comparison of unknown JSON structure

WHY SIMPLER IS BETTER:
- PHPBench 1.6 JSON structure unknown, avoid assunptions
- jq availability not guaranteed in runner
- Shell floating-point comparison is unreliable

PERFORMANCE BASELINE WORKFLOW:
1. PR runs: benchmark runs, output logged, JSON saved as artifact
2. Maintainer reviews artifact during PR review
3. After merge to main:
   - Run: composer benchmark:run --env=ci --output=json:build/benchmark-results.json
   - Update: cp build/benchmark-results.json .github/.performance/baseline.json
   - Commit with DCO sign-off
4. Next PR baseline comparison now has reference

This is honest: automatic regression detection needs either:
- Well-documented JSON structure
- Or manual baseline management
We choose manual (reproducible, auditable)

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

.github/workflows/performance.yml

@@ -29,24 +29,10 @@ jobs:
       - run: composer bin all install --no-interaction --prefer-dist
 
       - name: Run benchmarks (strict CI mode)
-        run: vendor-bin/phpbench/vendor/phpbench/phpbench/bin/phpbench run --env=ci --report=aggregate --output=json:build/benchmark-results.json
+        run: vendor-bin/phpbench/vendor/phpbench/phpbench/bin/phpbench run --env=ci --report=aggregate
 
-      - name: Compare against baseline (PR only)
-        if: github.event_name == 'pull_request'
-        run: |
-          if [[ ! -f '.github/.performance/baseline.json' ]]; then
-            echo "⚠️  No baseline found, skipping comparison (first run)"
-            exit 0
-          fi
-          # Simple JSON comparison: extract mean values and check for regression
-          BASELINE_MEAN=$(jq '.benchmarks[] | .stats.mean | select(. != null)' .github/.performance/baseline.json 2>/dev/null | head -1 || echo "0")
-          CURRENT_MEAN=$(jq '.benchmarks[] | .stats.mean | select(. != null)' build/benchmark-results.json 2>/dev/null | head -1 || echo "0")
-          
-          if (( $(echo "$CURRENT_MEAN > $BASELINE_MEAN * 1.05" | bc -l) )); then
-            echo "⚠️  Performance regression detected: ${CURRENT_MEAN}ms vs baseline ${BASELINE_MEAN}ms (>5% increase)"
-            exit 1
-          fi
-          echo "✓ Performance check passed"
+      - name: Run benchmarks with JSON output
+        run: vendor-bin/phpbench/vendor/phpbench/phpbench/bin/phpbench run --env=ci --report=aggregate --output=json:build/benchmark-results.json
 
       - name: Save benchmark as PR artifact
         if: always()