builder/vm: stabilize json_lint_vm under unified calls

- Fix condition_fn resolution: Value call path + dev safety + stub injection
- VM bridge: handle Method::birth via BoxCall; ArrayBox push/get/length/set direct bridge
- Receiver safety: pin receiver in method_call_handlers to avoid undefined use across blocks
- Local vars: materialize on declaration (use init ValueId; void for uninit)
- Prefer legacy BoxCall for Array/Map/String/user boxes in emit_box_or_plugin_call (stability-first)
- Test runner: update LLVM hint to llvmlite harness (remove LLVM_SYS_180_PREFIX guidance)
- Docs/roadmap: update CURRENT_TASK with unified default-ON + guards

Note: NYASH_DEV_BIRTH_INJECT_BUILTINS=1 can re-enable builtin birth() injection during migration.

tools/dev/check_builder_layers.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+root_dir="$(git rev-parse --show-toplevel 2>/dev/null || pwd)"
+cd "$root_dir"
+
+viol=0
+
+echo "[guard] Checking builder layer dependencies (origin→observe→rewrite)"
+
+# Rule 1: origin/* must NOT import observe or rewrite
+while IFS= read -r -d '' f; do
+  if rg -n "use\\s+crate::mir::builder::(observe|rewrite)" "$f" >/dev/null; then
+    echo "[ERROR] origin-layer import violation: $f"
+    rg -n "use\\s+crate::mir::builder::(observe|rewrite)" "$f" || true
+    viol=$((viol+1))
+  fi
+done < <(find src/mir/builder/origin -type f -name '*.rs' -print0 2>/dev/null || true)
+
+# Rule 2: observe/* must NOT import rewrite or origin
+while IFS= read -r -d '' f; do
+  if rg -n "use\\s+crate::mir::builder::(rewrite|origin)" "$f" >/dev/null; then
+    echo "[ERROR] observe-layer import violation: $f"
+    rg -n "use\\s+crate::mir::builder::(rewrite|origin)" "$f" || true
+    viol=$((viol+1))
+  fi
+done < <(find src/mir/builder/observe -type f -name '*.rs' -print0 2>/dev/null || true)
+
+# Rule 3: rewrite/* must NOT import origin (observe is allowed)
+while IFS= read -r -d '' f; do
+  if rg -n "use\\s+crate::mir::builder::origin" "$f" >/dev/null; then
+    echo "[ERROR] rewrite-layer import violation: $f"
+    rg -n "use\\s+crate::mir::builder::origin" "$f" || true
+    viol=$((viol+1))
+  fi
+done < <(find src/mir/builder/rewrite -type f -name '*.rs' -print0 2>/dev/null || true)
+
+if [[ $viol -gt 0 ]]; then
+  echo "[guard] FAILED: $viol violation(s) detected"
+  exit 1
+else
+  echo "[guard] OK: No violations"
+fi
+