Phase 11.8/12: MIR Core-13 roadmap, Nyash ABI design, async/await enhancements with TaskGroupBox foundation

Major additions:
- Phase 11.8 MIR cleanup specification (Core-15→14→13 roadmap)
- Nyash ABI unified design document (3×u64 structure)
- TaskGroupBox foundation with cancelAll/joinAll methods
- Enhanced async/await with checkpoint auto-insertion
- Structured concurrency preparation (parent-child task relationships)

Documentation:
- docs/development/roadmap/phases/phase-11.8_mir_cleanup/: Complete Core-13 path
- docs/development/roadmap/phases/phase-12/NYASH-ABI-DESIGN.md: Unified ABI spec
- Updated Phase 12 README with AOT/JIT explanation for script performance
- Added async_task_system/ design docs

Implementation progress:
- FutureBox spawn tracking with weak/strong reference management
- VM checkpoint integration before/after await
- LLVM backend async support preparation
- Verifier rules for await-checkpoint enforcement
- Result<T,E> normalization for timeout/cancellation

Technical insights:
- MIR as 'atomic instructions', Box as 'molecules' philosophy
- 'Everything is Box' enables full-stack with minimal instructions
- Unified BoxCall for array/plugin/async operations future consolidation

Next steps:
- Complete TaskGroupBox implementation
- Migrate from global to scoped task management
- Implement LIFO cleanup on scope exit
- Continue Core-13 instruction consolidation

🚀 'From 15 atoms to infinite programs: The Nyash Box Theory'

src/jit/lower/builder.rs

@@ -557,6 +557,8 @@ use super::extern_thunks::{
 };
 #[cfg(feature = "cranelift-jit")]
 use crate::jit::r#extern::r#async::nyash_future_await_h;
+#[cfg(feature = "cranelift-jit")]
+use crate::jit::r#extern::result::{nyash_result_ok_h, nyash_result_err_h};
 
 #[cfg(feature = "cranelift-jit")]
 use crate::{
@@ -1941,9 +1943,13 @@ impl CraneliftBuilder {
             builder.symbol("nyash.jit.dbg_i64", nyash_jit_dbg_i64 as *const u8);
             // Async/Future
             builder.symbol(crate::jit::r#extern::r#async::SYM_FUTURE_AWAIT_H, nyash_future_await_h as *const u8);
+            builder.symbol(crate::jit::r#extern::result::SYM_RESULT_OK_H, nyash_result_ok_h as *const u8);
+            builder.symbol(crate::jit::r#extern::result::SYM_RESULT_ERR_H, nyash_result_err_h as *const u8);
             builder.symbol("nyash.jit.block_enter", nyash_jit_block_enter as *const u8);
             // Async/Future
             builder.symbol(crate::jit::r#extern::r#async::SYM_FUTURE_AWAIT_H, nyash_future_await_h as *const u8);
+            builder.symbol(crate::jit::r#extern::result::SYM_RESULT_OK_H, nyash_result_ok_h as *const u8);
+            builder.symbol(crate::jit::r#extern::result::SYM_RESULT_ERR_H, nyash_result_err_h as *const u8);
             builder.symbol("nyash.jit.dbg_i64", nyash_jit_dbg_i64 as *const u8);
         {
             use crate::jit::r#extern::collections as c;