Phase 11-12: LLVM backend initial, semantics layer, plugin unification

Major changes:
- LLVM backend initial implementation (compiler.rs, llvm mode)
- Semantics layer integration in interpreter (operators.rs)
- Phase 12 plugin architecture revision (3-layer system)
- Builtin box removal preparation
- MIR instruction set documentation (26→Core-15 migration)
- Cross-backend testing infrastructure
- Await/nowait syntax support

New features:
- LLVM AOT compilation support (--backend llvm)
- Semantics layer for interpreter→VM flow
- Tri-backend smoke tests
- Plugin-only registry mode

Bug fixes:
- Interpreter plugin box arithmetic operations
- Branch test returns incorrect values

Documentation:
- Phase 12 README.md updated with new plugin architecture
- Removed obsolete NYIR proposals
- Added LLVM test programs documentation

Co-Authored-By: Claude <noreply@anthropic.com>

tools/build_llvm.ps1

@@ -0,0 +1,60 @@
+#!/usr/bin/env pwsh
+param(
+  [Parameter(Mandatory=$true, Position=0)][string]$NyashFile,
+  [Parameter(Mandatory=$false)][string]$Out = "app.exe"
+)
+
+# Build + link AOT on Windows (MSVC or MinGW)
+# Requirements:
+# - LLVM 18 installed (clang/lld in PATH). Optionally set LLVM_SYS_180_PREFIX
+# - Rust toolchain for Windows (default host)
+# - This repo builds with `--features llvm`
+
+$ErrorActionPreference = 'Stop'
+
+function Info($msg) { Write-Host "[build-llvm.ps1] $msg" -ForegroundColor Cyan }
+function Err($msg) { Write-Host "[build-llvm.ps1] ERROR: $msg" -ForegroundColor Red; exit 1 }
+
+# Ensure object dir exists
+$objDir = Join-Path $PSScriptRoot "..\target\aot_objects"
+New-Item -ItemType Directory -Path $objDir -Force | Out-Null
+$objPath = Join-Path $objDir ("{0}.o" -f ([IO.Path]::GetFileNameWithoutExtension($Out)))
+
+# Build nyash with LLVM backend
+Info "Building nyash (release, feature=llvm)"
+if ($env:LLVM_SYS_181_PREFIX) { Info "LLVM_SYS_181_PREFIX=$($env:LLVM_SYS_181_PREFIX)" }
+elseif ($env:LLVM_SYS_180_PREFIX) { Info "LLVM_SYS_180_PREFIX=$($env:LLVM_SYS_180_PREFIX)" }
+cargo build --release --features llvm | Out-Null
+
+# Emit object from the Nyash program
+Remove-Item -ErrorAction SilentlyContinue $objPath
+Info "Emitting object: $objPath from $NyashFile"
+$env:NYASH_LLVM_OBJ_OUT = (Resolve-Path $objPath)
+if (-not $env:LLVM_SYS_181_PREFIX -and $env:LLVM_SYS_180_PREFIX) { $env:LLVM_SYS_181_PREFIX = $env:LLVM_SYS_180_PREFIX }
+& .\target\release\nyash.exe --backend llvm $NyashFile | Out-Null
+if (!(Test-Path $objPath)) { Err "Object not generated: $objPath" }
+if ((Get-Item $objPath).Length -le 0) { Err "Object is empty: $objPath" }
+
+# Build NyRT static library for current host
+Info "Building NyRT (static lib)"
+cargo build -p nyrt --release | Out-Null
+
+# Try MSVC first (.lib), then MinGW (.a)
+$nyrtLibMSVC = Join-Path $PSScriptRoot "..\target\release\nyrt.lib"
+$nyrtLibGNU  = Join-Path $PSScriptRoot "..\target\release\libnyrt.a"
+
+if (Test-Path $nyrtLibMSVC) {
+  Info "Linking (MSVC): $Out"
+  # Use clang/lld to link COFF obj + .lib
+  & clang -fuse-ld=lld -o $Out $objPath $nyrtLibMSVC 2>$null
+}
+elseif (Test-Path $nyrtLibGNU) {
+  Info "Linking (MinGW): $Out"
+  & clang -o $Out $objPath $nyrtLibGNU -static 2>$null
+}
+else {
+  Err "NyRT static library not found (expected nyrt.lib or libnyrt.a)"
+}
+
+if (!(Test-Path $Out)) { Err "Link failed: $Out not found" }
+Info ("OK: built {0} ({1} bytes)" -f $Out, (Get-Item $Out).Length)