Phase 21.6 solidification: chain green (return/binop/loop/call); add Phase 21.7 normalization plan (methodize static boxes). Update CURRENT_TASK.md and docs.

docs/development/roadmap/phases/phase-21.7-normalization/CHECKLIST.md

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+Phase 21.7 — Normalization Checklist (Methodization)
+
+Targets (must be green)
+- Naming: all user functions canonicalized as Box.method/N
+- Arity: params.len == call.args.len (or explicit mapping when defs absent)
+- Methodization (dev toggle): Global("Box.method") → Method(receiver=static singleton)
+- VM: Method calls execute via ensure_static_box_instance for static boxes
+- LLVM: mir_call(Method) lowering produces correct IR; rc parity preserved
+
+Canaries
+- tools/dev/phase216_chain_canary_call.sh — remains PASS when OFF, PASS when ON
+- Add: tools/dev/phase217_methodize_canary.sh (dev) — asserts method callee usage in MIR or IR tags
+
+Toggles
+- HAKO_MIR_BUILDER_METHODIZE=1 (new)
+- HAKO_STAGEB_FUNC_SCAN=1 / HAKO_MIR_BUILDER_FUNCS=1 / HAKO_MIR_BUILDER_CALL_RESOLVE=1 (existing)
+
+Rollback
+- Disable HAKO_MIR_BUILDER_METHODIZE; remove methodization rewrite; keep Global path active.
+

docs/development/roadmap/phases/phase-21.7-normalization/README.md

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+Phase 21.7 — Normalization & Unification (Methodize Static Boxes)
+
+Goal
+- Unify user-defined function calls onto a single, consistent representation.
+- Move from ad-hoc Global("Box.method") calls toward Method calls with an explicit (singleton) receiver when appropriate.
+- Keep defaults stable; introduce dev toggles and canaries; then promote to default after green.
+
+Scope
+- Parser/Stage‑B: keep emitting Program(JSON v0). No schema changes required for MVP.
+- MirBuilder: add methodization (dev toggle) that:
+  - Emits method functions as-is (defs) and/or provides a mapping to Method calls
+  - Rewrites Global("Box.method") to Method {receiver=static singleton, box_name, method}
+  - Preserves arity and naming as Box.method/N
+- VM: handle Method calls uniformly (receiver resolved via ensure_static_box_instance for static boxes).
+- LLVM: rely on mir_call(Method) lowering (already supported) and provide the static receiver where needed.
+
+Toggles
+- HAKO_MIR_BUILDER_METHODIZE=1 — enable methodization (rewrite Global→Method with static singleton receiver)
+- HAKO_STAGEB_FUNC_SCAN=1 — Stage‑B defs scan (already available)
+- HAKO_MIR_BUILDER_FUNCS=1 — defs→MIR 関数化（既存）
+- HAKO_MIR_BUILDER_CALL_RESOLVE=1 — Global 名解決（既存）
+
+Design Rules
+- Naming: canonical "Box.method/N". Arity N must equal params.len (or callsite args len if defs unknown).
+- Receiver: for static boxes, provide implicit singleton receiver. For instance boxes, preserve existing Method path.
+- Effects: preserve EffectMask semantics; do not broaden side effects.
+- Fail‑Fast: when rewrite is ambiguous (multiple candidates), keep original form and WARN under dev toggle; never change defaults silently.
+
+Acceptance
+- Canaries:
+  - call (global style) passes when methodization ON (rc unchanged)
+  - Existing return/binop/loop/call (global) canaries remain green when OFF
+  - A dedicated methodization canary asserts presence of callee.type=="Method" in MIR(JSON v1) or correct v0 lowering
+
+Rollout Plan
+1) Ship behind HAKO_MIR_BUILDER_METHODIZE=1 with canaries
+2) Validate on representative apps (selfhost‑first path)
+3) Promote to default ON only after green for a cycle; keep rollback instructions
+
+Rollback
+- Disable HAKO_MIR_BUILDER_METHODIZE. Revert to Global("Box.method") resolution path (current 21.6 behavior).
+