Debug Counters Implementation - Clean History

Major Features:
- Debug counter infrastructure for Refill Stage tracking
- Free Pipeline counters (ss_local, ss_remote, tls_sll)
- Diagnostic counters for early return analysis
- Unified larson.sh benchmark runner with profiles
- Phase 6-3 regression analysis documentation

Bug Fixes:
- Fix SuperSlab disabled by default (HAKMEM_TINY_USE_SUPERSLAB)
- Fix profile variable naming consistency
- Add .gitignore patterns for large files

Performance:
- Phase 6-3: 4.79 M ops/s (has OOM risk)
- With SuperSlab: 3.13 M ops/s (+19% improvement)

This is a clean repository without large log files.

🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>

scripts/verify_fast_cap_0_bug.sh

@@ -0,0 +1,67 @@
+#!/bin/bash
+# Verification script for FAST_CAP=0 SEGV bug
+# Usage: ./scripts/verify_fast_cap_0_bug.sh
+
+set -e
+
+echo "============================================"
+echo "FAST_CAP=0 SEGV Bug Verification"
+echo "============================================"
+echo ""
+
+# Build with debug if needed
+if [ ! -f libhakmem.so ]; then
+    echo "[Step 1] Building libhakmem.so..."
+    make clean && make
+    echo ""
+fi
+
+echo "[Step 2] Single-threaded test (should PASS)..."
+HAKMEM_TINY_FAST_CAP=0 \
+HAKMEM_LARSON_TINY_ONLY=1 \
+HAKMEM_TINY_USE_SUPERSLAB=1 \
+timeout 5 ./larson_hakmem 2 8 128 1024 1 12345 1 && echo "✓ PASSED" || echo "✗ FAILED"
+echo ""
+
+echo "[Step 3] Multi-threaded test (expected to CRASH)..."
+HAKMEM_TINY_FAST_CAP=0 \
+HAKMEM_LARSON_TINY_ONLY=1 \
+HAKMEM_TINY_USE_SUPERSLAB=1 \
+HAKMEM_TINY_TRACE_RING=1 \
+timeout 5 ./larson_hakmem 2 8 128 1024 1 12345 4 2>&1 | tee /tmp/hakmem_crash.log && echo "✓ PASSED (unexpected!)" || echo "✗ CRASHED (expected)"
+echo ""
+
+echo "[Step 4] Checking Debug Ring output..."
+if grep -q "remote_drain" /tmp/hakmem_crash.log; then
+    echo "✓ remote_drain events found (Fix is working!)"
+else
+    echo "✗ NO remote_drain events (confirms diagnosis)"
+fi
+echo ""
+
+echo "[Step 5] Checking for remote_push events..."
+if grep -q "remote_push" /tmp/hakmem_crash.log; then
+    echo "✓ remote_push events found (cross-thread frees happening)"
+else
+    echo "✗ NO remote_push events (unexpected)"
+fi
+echo ""
+
+echo "[Step 6] Testing with FAST_CAP=64 (should PASS)..."
+HAKMEM_TINY_FAST_CAP=64 \
+HAKMEM_LARSON_TINY_ONLY=1 \
+HAKMEM_TINY_USE_SUPERSLAB=1 \
+timeout 5 ./larson_hakmem 2 8 128 1024 1 12345 4 && echo "✓ PASSED" || echo "✗ FAILED (unexpected!)"
+echo ""
+
+echo "============================================"
+echo "Verification Complete"
+echo "============================================"
+echo ""
+echo "Expected results:"
+echo "  - Single-thread: PASS"
+echo "  - Multi-thread FAST_CAP=0: CRASH (no remote_drain)"
+echo "  - Multi-thread FAST_CAP=64: PASS"
+echo ""
+echo "See /tmp/hakmem_crash.log for crash details"
+echo "See FAST_CAP_0_SEGV_ROOT_CAUSE_ANALYSIS.md for full analysis"