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/opt/readme.md

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+# selfhost/opt — Optimization/Preparation Boxes
+
+Purpose
+- Provide small, opt-in preparation/optimization stages implemented in Hakorune.
+- First step: AotPrepBox — MIR(JSON) normalize + safe local const-fold for single-block const/binop/ret.
+
+Responsibilities
+- JSON normalization via shared MirIoBox (canonicalization hook).
+- Behavior-preserving, local transforms only; Fail‑Fast for unsupported shapes.
+
+Non-Responsibilities
+- Global CFG rewrites, SSA rebuild, or MIR semantics changes.
+
+Gates
+- Runner uses HAKO_AOT_PREP=1 to save “prepared” MIR sidecar after emit‑exe.
+- Later we may switch compile input behind a dedicated flag once stable.
+