restore(lang): full lang tree from ff3ef452 (306 files) — compiler, vm, shared, runner, c-abi, etc.\n\n- Restores lang/ directory (files≈306, dirs≈64) as per historical branch with selfhost sources\n- Keeps our recent parser index changes in compiler/* (merged clean by checkout)\n- Unblocks selfhost development and documentation references

lang/src/tools/vm_front/LAYER_GUARD.hako

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+#![doc = "Phase 20.13 vm_front guard — define layer responsibilities."]
+
+static box VM_FRONT_GUARD {
+  name() { return "vm_front" }
+  allowed_imports() { return ["json", "env"] }
+  forbidden_imports() { return ["vm_core", "llvm", "plugins", "ffi"] }
+}
+

lang/src/tools/vm_front/README.md

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+# vm_front — VM Front EXE (Phase 20.13; optional)
+
+Purpose
+- Provide light dispatch hints/normalization prior to VM/LLVM execution.
+- Keep semantics in VM/LLVM; vm_front only shapes inputs and rejects invalid cases early.
+
+Responsibilities
+- Normalize callee/method hints; produce OK/NOOP/FAIL (short) with exit code.
+
+Notes (AOT / Single‑EXE)
+- 将来的に単一exeに内蔵（AOT）され、同一プロセスで前段整流を行います。
+- 開発時は tools/front_exe/vm_front.sh をゲートONで差し替え可能です。
+
+Inputs/Outputs
+- Input: small JSON describing callsite/callee
+- Output: one-line verdict (OK/NOOP/FAIL) + exit code
+
+ENV (planned; default OFF)
+- HAKO_VM_USE_SCRIPT_EXE=1 (alias NYASH_*) — enable vm front EXE
+- HAKO_QUIET=1
+
+Non‑Goals
+- No execution, no state, no ABI interaction.
+
+TTL
+- Runner-side formatting will migrate here after stabilization.