Phase 21.7 normalization: optimization pre-work + bench harness expansion

- Add opt-in optimizations (defaults OFF)
  - Ret purity verifier: NYASH_VERIFY_RET_PURITY=1
  - strlen FAST enhancement for const handles
  - FAST_INT gate for same-BB SSA optimization
  - length cache for string literals in llvmlite
- Expand bench harness (tools/perf/microbench.sh)
  - Add branch/call/stringchain/arraymap/chip8/kilo cases
  - Auto-calculate ratio vs C reference
  - Document in benchmarks/README.md
- Compiler health improvements
  - Unify PHI insertion to insert_phi_at_head()
  - Add NYASH_LLVM_SKIP_BUILD=1 for build reuse
- Runtime & safety enhancements
  - Clarify Rust/Hako ownership boundaries
  - Strengthen receiver localization (LocalSSA/pin/after-PHIs)
  - Stop excessive PluginInvoke→BoxCall rewrites
- Update CURRENT_TASK.md, docs, and canaries

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

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

tools/dev/phase217_method_norm_canary.sh

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT=$(CDPATH= cd -- "$(dirname -- "$0")/../.." && pwd)
+cd "$ROOT"
+
+TMP_SRC=$(mktemp --suffix .hako)
+cat >"$TMP_SRC" <<'HAKO'
+static box Main {
+  method add(a,b){ return a + b }
+  method main(){ return add(2,3) }
+}
+HAKO
+
+TMP_JSON=$(mktemp --suffix .json)
+
+# Emit MIR(JSON) with defs + call resolution
+HAKO_SELFHOST_BUILDER_FIRST=1 HAKO_STAGEB_FUNC_SCAN=1 HAKO_MIR_BUILDER_FUNCS=1 HAKO_MIR_BUILDER_CALL_RESOLVE=1 \
+  bash "$ROOT/tools/hakorune_emit_mir.sh" "$TMP_SRC" "$TMP_JSON" >/dev/null
+
+# Check that names include arity suffix '/2'
+if ! rg -q '"name"\s*:\s*"Main.add/2"' "$TMP_JSON"; then
+  echo "[FAIL] missing arity-suffixed function name Main.add/2" >&2
+  exit 1
+fi
+if ! rg -q '"value"\s*:\s*"Main.add/2"' "$TMP_JSON"; then
+  echo "[FAIL] missing arity-suffixed call target Main.add/2" >&2
+  exit 1
+fi
+
+# Build and run EXE (crate)
+NYASH_LLVM_BACKEND=crate NYASH_LLVM_SKIP_BUILD=1 \
+NYASH_NY_LLVM_COMPILER="${NYASH_NY_LLVM_COMPILER:-$ROOT/target/release/ny-llvmc}" \
+NYASH_EMIT_EXE_NYRT="${NYASH_EMIT_EXE_NYRT:-$ROOT/target/release}" \
+  bash "$ROOT/tools/ny_mir_builder.sh" --in "$TMP_JSON" --emit exe -o /tmp/phase217_norm.exe --quiet >/dev/null
+
+set +e
+/tmp/phase217_norm.exe; rc=$?
+set -e
+[[ "$rc" == "5" ]] && echo "[PASS] phase217_method_norm (rc=5, arity suffix present)" || { echo "[FAIL] rc=$rc" >&2; exit 1; }
+
+rm -f "$TMP_SRC" "$TMP_JSON" /tmp/phase217_norm.exe 2>/dev/null || true
+exit 0