Phase 83-1 + Allocator Comparison: Switch dispatch fixed (NO-GO +0.32%), PROFILE correction, SCORECARD update

Key changes:
- Phase 83-1: Switch dispatch fixed mode (tiny_inline_slots_switch_dispatch_fixed_box) - NO-GO (marginal +0.32%, branch reduction negligible)
  Reason: lazy-init pattern already optimal, Phase 78-1 pattern shows diminishing returns

- Allocator comparison baseline update (10-run SSOT, WS=400, ITERS=20M):
  tcmalloc: 115.26M (92.33% of mimalloc)
  jemalloc: 97.39M (77.96% of mimalloc)
  system: 85.20M (68.24% of mimalloc)
  mimalloc: 124.82M (baseline)

- hakmem PROFILE correction: scripts/run_mixed_10_cleanenv.sh + run_allocator_quick_matrix.sh
  PROFILE explicitly set to MIXED_TINYV3_C7_SAFE for hakmem measurements
  Result: baseline stabilized to 55.53M (44.46% of mimalloc)
  Previous unstable measurement (35.57M) was due to profile leak

- Documentation:
  * PERFORMANCE_TARGETS_SCORECARD.md: Reference allocators + M1/M2 milestone status
  * PHASE83_1_SWITCH_DISPATCH_FIXED_RESULTS.md: Phase 83-1 analysis (NO-GO)
  * ALLOCATOR_COMPARISON_QUICK_RUNBOOK.md: Quick comparison procedure
  * ALLOCATOR_COMPARISON_SSOT.md: Detailed SSOT methodology

- M2 milestone status: 44.46% (target 55%, gap -10.54pp) - structural improvements needed

🤖 Generated with Claude Code
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

docs/analysis/PHASE80_INLINE_SLOTS_SWITCH_DISPATCH_1_RESULTS.md

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+# Phase 80-1: Inline Slots Switch Dispatch — Results
+
+## Goal
+
+Reduce per-op comparison/branch overhead in inline-slots routing for the hot classes by replacing the sequential `if (class_idx==X)` chain with a `switch (class_idx)` dispatch when enabled.
+
+Scope:
+- Alloc hot path: `core/box/tiny_front_hot_box.h`
+- Free legacy fallback: `core/box/tiny_legacy_fallback_box.h`
+
+## Change Summary
+
+- New env gate box: `core/box/tiny_inline_slots_switch_dispatch_box.h`
+  - ENV: `HAKMEM_TINY_INLINE_SLOTS_SWITCHDISPATCH=0/1` (default 0)
+- When enabled, uses switch dispatch for C4/C5/C6 (and excludes C2/C3 work, which is NO-GO).
+- Reversible: set `HAKMEM_TINY_INLINE_SLOTS_SWITCHDISPATCH=0` to restore the original if-chain.
+
+## A/B (Mixed SSOT, 10-run)
+
+Workload:
+- `ITERS=20000000`, `WS=400`, `RUNS=10`
+- `scripts/run_mixed_10_cleanenv.sh`
+
+Results:
+
+Baseline (SWITCHDISPATCH=0, if-chain):
+- Mean: `51.98M ops/s`
+
+Treatment (SWITCHDISPATCH=1, switch):
+- Mean: `52.84M ops/s`
+
+Delta:
+- `+1.65%` ✅ **GO** (threshold +1.0%)
+
+## perf stat (single-run sanity)
+
+Key deltas (treatment vs baseline):
+- Cycles: `-1.6%`
+- Instructions: `-1.5%`
+- Branches: `-2.9%` ✅
+- Cache-misses: `-6.7%`
+- Throughput (single): `+3.7%`
+
+Interpretation:
+- Switch dispatch removes repeated failed comparisons for the hot inline-slot classes, reducing branches/instructions without causing cache-miss explosions.
+
+## Promotion
+
+Promoted to Mixed SSOT defaults:
+- `core/bench_profile.h`: `HAKMEM_TINY_INLINE_SLOTS_SWITCHDISPATCH=1`
+- `scripts/run_mixed_10_cleanenv.sh`: `HAKMEM_TINY_INLINE_SLOTS_SWITCHDISPATCH=1`
+
+Rollback:
+```sh
+export HAKMEM_TINY_INLINE_SLOTS_SWITCHDISPATCH=0
+```
+