fix: Windows cross-compilation support (GOOS=windows)

- debugcli.go/debugtui.go: add //go:build !windows tag
- debugcli_windows.go/debugtui_windows.go: no-op stubs
- cdx/cdx.go: extract mmap to platform-specific files
- cdx/mmap_posix.go: syscall.Mmap/Munmap
- cdx/mmap_windows.go: no-op (falls back to read)
- ntx/ntx.go, ntx/build.go: same mmap extraction
- ntx/mmap_posix.go, ntx/mmap_windows.go: platform split

Builds verified: linux/amd64, windows/amd64, darwin/arm64, darwin/amd64

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hbrdd/cdx/cdx.go

@@ -24,7 +24,6 @@ import (
 	"os"
 	"sort"
 	"strings"
-	"syscall"
 )
 
 // CDX constants — matching Harbour.
@@ -357,10 +356,9 @@ func OpenIndex(path string) (*Index, error) {
 
 	idx := &Index{file: f}
 
-	// mmap for zero-copy reads
+	// mmap for zero-copy reads (platform-specific, no-op on Windows)
 	if fi, err2 := f.Stat(); err2 == nil && fi.Size() > 0 {
-		if data, err2 := syscall.Mmap(int(f.Fd()), 0, int(fi.Size()),
-			syscall.PROT_READ, syscall.MAP_SHARED); err2 == nil {
+		if data, err2 := mmapFile(f, int(fi.Size())); err2 == nil {
 			idx.mmapData = data
 		}
 	}
@@ -420,7 +418,7 @@ func OpenIndex(path string) (*Index, error) {
 // Close closes the CDX file.
 func (idx *Index) Close() error {
 	if idx.mmapData != nil {
-		syscall.Munmap(idx.mmapData)
+		munmapFile(idx.mmapData)
 		idx.mmapData = nil
 	}
 	return idx.file.Close()

hbrdd/cdx/mmap_posix.go

@@ -0,0 +1,16 @@
+//go:build !windows
+
+package cdx
+
+import (
+	"os"
+	"syscall"
+)
+
+func mmapFile(f *os.File, size int) ([]byte, error) {
+	return syscall.Mmap(int(f.Fd()), 0, size, syscall.PROT_READ, syscall.MAP_SHARED)
+}
+
+func munmapFile(data []byte) error {
+	return syscall.Munmap(data)
+}

hbrdd/cdx/mmap_windows.go

@@ -0,0 +1,17 @@
+//go:build windows
+
+package cdx
+
+import (
+	"errors"
+	"os"
+)
+
+// Windows: mmap not implemented — fallback to read() path.
+func mmapFile(f *os.File, size int) ([]byte, error) {
+	return nil, errors.New("mmap not supported on Windows")
+}
+
+func munmapFile(data []byte) error {
+	return nil
+}

hbrdd/ntx/build.go

@@ -9,7 +9,6 @@ import (
 	"fmt"
 	"os"
 	"sort"
-	"syscall"
 )
 
 // KeyRecord pairs a key value with its record number for sorting.
@@ -487,7 +486,7 @@ func encodeInternalPage(children []*buildPage, keyLen, itemSize, maxItem int, of
 func (idx *Index) insertKeyBTree(key []byte, recNo uint32) error {
 	// Disable mmap during insertion (file grows, mmap stale)
 	if idx.mmapData != nil {
-		syscall.Munmap(idx.mmapData)
+		munmapFile(idx.mmapData)
 		idx.mmapData = nil
 	}
 	// Search for insertion position

hbrdd/ntx/mmap_posix.go

@@ -0,0 +1,16 @@
+//go:build !windows
+
+package ntx
+
+import (
+	"os"
+	"syscall"
+)
+
+func mmapFile(f *os.File, size int) ([]byte, error) {
+	return syscall.Mmap(int(f.Fd()), 0, size, syscall.PROT_READ, syscall.MAP_SHARED)
+}
+
+func munmapFile(data []byte) error {
+	return syscall.Munmap(data)
+}

hbrdd/ntx/mmap_windows.go

@@ -0,0 +1,16 @@
+//go:build windows
+
+package ntx
+
+import (
+	"errors"
+	"os"
+)
+
+func mmapFile(f *os.File, size int) ([]byte, error) {
+	return nil, errors.New("mmap not supported on Windows")
+}
+
+func munmapFile(data []byte) error {
+	return nil
+}

hbrdd/ntx/ntx.go

@@ -16,7 +16,6 @@ import (
 	"fmt"
 	"os"
 	"strings"
-	"syscall"
 )
 
 // NTX constants — matching Harbour exactly.
@@ -268,8 +267,7 @@ func (idx *Index) mmapFile() {
 	if err != nil || fi.Size() < HeaderSize {
 		return
 	}
-	data, err := syscall.Mmap(int(idx.file.Fd()), 0, int(fi.Size()),
-		syscall.PROT_READ, syscall.MAP_SHARED)
+	data, err := mmapFile(idx.file, int(fi.Size()))
 	if err != nil {
 		return // fallback to file reads
 	}
@@ -280,7 +278,7 @@ func (idx *Index) mmapFile() {
 // Also invalidates page pool (data slices pointed into old mmap).
 func (idx *Index) remapFile() {
 	if idx.mmapData != nil {
-		syscall.Munmap(idx.mmapData)
+		munmapFile(idx.mmapData)
 		idx.mmapData = nil
 	}
 	// Invalidate page pool — data slices pointed into old mmap
@@ -295,7 +293,7 @@ func (idx *Index) TestGetMmap() []byte { return idx.mmapData }
 
 func (idx *Index) Close() error {
 	if idx.mmapData != nil {
-		syscall.Munmap(idx.mmapData)
+		munmapFile(idx.mmapData)
 		idx.mmapData = nil
 	}
 	return idx.file.Close()

hbrt/debugcli.go

@@ -1,3 +1,5 @@
+//go:build !windows
+
 // Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
 // All rights reserved.
 

hbrt/debugcli_windows.go

@@ -0,0 +1,13 @@
+//go:build windows
+
+package hbrt
+
+import "fmt"
+
+// CLIDebugger returns a no-op debug callback on Windows.
+func CLIDebugger() DebugCallback {
+	return func(event *DebugEvent) int {
+		fmt.Println("[debugger not available on Windows]")
+		return 0 // continue
+	}
+}

hbrt/debugtui.go

@@ -1,3 +1,5 @@
+//go:build !windows
+
 // Copyright (c) 2026 Charles KWON OhJun (charleskwonohjun@gmail.com)
 // All rights reserved.
 

hbrt/debugtui_windows.go

@@ -0,0 +1,13 @@
+//go:build windows
+
+package hbrt
+
+import "fmt"
+
+// TUIDebugger returns a no-op debug callback on Windows.
+func TUIDebugger() DebugCallback {
+	return func(event *DebugEvent) int {
+		fmt.Println("[TUI debugger not available on Windows]")
+		return 0 // continue
+	}
+}