MIR Builder Modules (Current Split)

This note summarizes the current split of the MIR builder to keep builder.rs thin and maintainable.

Paths:

src/mir/builder.rs: Thin hub for MIR building; owns state (generators, maps) and high‑level coordination.
src/mir/builder/stmts.rs: Statement builders
- build_print_statement, build_block, build_if_statement, build_loop_statement, build_try_catch_statement, build_throw_statement, build_local_statement, build_return_statement, build_nowait_statement, build_await_expression, build_me_expression.
src/mir/builder/ops.rs: Expression ops
- build_binary_op, build_unary_op, convert_binary_operator, convert_unary_operator.
src/mir/builder/utils.rs: Shared utilities
- resolve_include_path_builder, builder_debug_enabled, builder_debug_log, infer_type_from_phi.
Calls: src/mir/builder/builder_calls.rs
- build_function_call, build_method_call, build_from_expression, lower_method_as_function, lower_static_method_as_function, parse_type_name_to_mir, extract_string_literal.

Notes:

builder.rs now stays < 1,000 LOC by delegating to the above modules.
No behavior change intended; only mechanical movement. jit‑direct smokes remain green.
Debug logs remain gated by NYASH_BUILDER_DEBUG=1.

Run checks:

Build (JIT): cargo build --release --features cranelift-jit
jit‑direct smokes:
- NYASH_JIT_THRESHOLD=1 ./target/release/nyash --jit-direct apps/tests/mir-branch-ret/main.hako
- NYASH_JIT_THRESHOLD=1 ./target/release/nyash --jit-direct apps/tests/mir-phi-min/main.hako
- NYASH_JIT_THRESHOLD=1 ./target/release/nyash --jit-direct apps/tests/mir-branch-multi/main.hako