Initial working shell: bash-for-windows

- Cross-compiled Go-based shell for Windows (PE32+ executable)
- Builtins: cd, pwd, echo, exit, export, source, alias, type
- Coreutils: ls, cat, grep, sort, wc, head, find, cp, mv, rm, mkdir, touch, clear
- Command chaining: &&, ||, ;
- Pipes between builtins and external commands
- Variable expansion (, ) and assignment (NAME=VALUE)
- Tokenizer with single/double quote handling
- Linux and Windows (x86_64) builds via build.sh

build.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+set -e
+
+BUILD_DIR="build"
+mkdir -p "$BUILD_DIR"
+
+echo "=== Building bash-for-windows ==="
+
+# Linux build
+echo "  -> Linux..."
+go build -ldflags="-s -w" -o "$BUILD_DIR/bash-windows" .
+
+# Windows cross-compile
+echo "  -> Windows (x86_64)..."
+GOOS=windows GOARCH=amd64 CGO_ENABLED=0 go build -ldflags="-s -w" -o "$BUILD_DIR/bash-windows.exe" .
+
+echo ""
+echo "=== Build complete ==="
+ls -lh "$BUILD_DIR/"