phase-21.9: add De‑Rust roadmap + phase plan; stage archive script for Rust LLVM backend (no move yet)

docs/development/strategies/de-rust-roadmap.md

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+# De‑Rust Roadmap (Phase 21.9+)
+
+Purpose: reduce Rust surface (non‑plugin) while keeping correctness and reversibility. Make Hakorune (Hako) the primary host for parsing/building/executing; keep Rust for kernel/ABI/thin wrappers.
+
+## Phases
+
+### Phase 0 — Archive (low risk)
+- Target: Rust LLVM backend (src/backend/llvm) — deprecated in favor of Python llvmlite.
+- Action: move to `archive/rust-llvm-backend/` with a clear RESTORE.md.
+- Acceptance: `cargo build --release` (default features) remains green; quick smokes green.
+- Revert: `git mv archive/rust-llvm-backend/llvm src/backend/`.
+
+### Phase 1 — Quick Wins (1–2 months)
+- hv1_inline → Hako parity (already functionally covered; keep as perf path).
+- MIR interpreter parity check; route Primary to Hako VM.
+- TLV codec → C shim (FFI) with thin Rust wrapper.
+- LLVM wrapper → Hako/C harness (Python stays primary until Hako IR is ready).
+
+### Phase 2 — Core Thinning (2–4 months)
+- Plugin loader thin C wrapper (dlopen/dlsym), unify host ABI.
+- Basic boxes (Array/Map/File) small C core (handle‑based), keep Rust shim.
+- Resolver/Using: SSOT in Hako; runner uses shared policy.
+
+### Phase 3 — Long‑haul (3–6 months)
+- Python llvmlite → Hako IR builder + C ABI.
+- Parser/MIR builder fully Hako‑first; Rust becomes fallback.
+- NyKernel minimal C runtime (BoxCall dispatcher + collections + file).
+
+## Principles
+- Guard everything by env/features; defaults unchanged.
+- Keep changes reversible (small diffs, RESTORE docs, fallbacks).
+- Test gates: quick smokes + representative hv1/hakovm parity.
+
+## Today (suggested)
+1) Stage Phase‑0 move as a script (not auto‑run) + RESTORE.md.
+2) Add phase docs (docs/private/roadmap/phases/phase-21.9/PLAN.md).
+3) Keep CI/dev instructions intact (no build break when features=none).
+