perf(typebox): reduce clones with Arc<str> for MethodSignature.name and TypeBox.methods keys; API kept stable. tools: add all-cases empty-PHI smoke runner. parser(box): extract birth_once cycle validation into helper

tools/test/smoke/llvm/ir_phi_empty_check_all.sh

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Run empty-PHI checker across a curated set of test cases
+CASES=(
+  apps/tests/hello_simple_llvm.nyash
+  apps/tests/loop_if_phi.nyash
+  apps/tests/llvm_phi_mix.nyash
+  apps/tests/llvm_phi_heavy_mix.nyash
+  apps/tests/llvm_phi_try_mix.nyash
+)
+
+DIR="tools/test/smoke/llvm"
+
+for c in "${CASES[@]}"; do
+  echo "[phi-empty-check-all] -> $c"
+  bash "$DIR/ir_phi_empty_check.sh" "$c"
+done
+
+echo "[phi-empty-check-all] OK: all cases passed"