Add Windows native watcher with Unix socket IPC

Architecture:
- Windows binary: watches files via ReadDirectoryChangesW (fsnotify),
  sends events as newline-delimited JSON over Unix domain socket
- Container: performs initial sync, then listens on socket for events
  from Windows watcher

New files:
- cmd_windows.go: Windows serve command (watcher + socket server)
- cmd_linux.go: Linux socket client + event listener
- types.go: shared FileEvent, FileMeta, Manifest types
- watcher_test_helper.go: inotify-based watcher for integration tests

Changes:
- main.go: simplified to just call run()
- watcher.go: removed fsnotify dependency, extracted Watcher interface
- sync.go: removed duplicate type definitions
- watcher_test.go: uses watchForTests() helper

Usage:
  sourcewatch.exe -dir C:\myproject -socket D:\sourcewatch.sock
  docker run -v D:\sourcewatch.sock:/run/sourcewatch.sock \
             -v C:\myproject:/host:ro -v mydata:/data sourcewatch

1 files changed, 250 insertions, 0 deletions

diff --git a/cmd_windows.go b/cmd_windows.go
new file mode 100644
index 0000000..b68851a
--- /dev/null
+++ b/cmd_windows.go
@@ -0,0 +1,250 @@
+//go:build windows
+
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"net"
+	"os"
+	"os/signal"
+	"path/filepath"
+	"sync"
+	"syscall"
+	"time"
+
+	"github.com/fsnotify/fsnotify"
+)
+
+var (
+	socketPath = flag.String("socket", "", "Unix socket path to serve events on (required)")
+	sourceDir  = flag.String("dir", "", "Source directory to watch (required)")
+)
+
+func run() {
+	flag.Parse()
+
+	if *socketPath == "" || *sourceDir == "" {
+		fmt.Fprintln(os.Stderr, "Usage: sourcewatch.exe -dir <source> -socket <socket-path>")
+		os.Exit(1)
+	}
+
+	level, err := ParseLogLevel(*logLevel)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(1)
+	}
+	SetLogLevel(level)
+
+	logInfo("watcher: starting on %s", *sourceDir)
+	logInfo("watcher: serving on %s", *socketPath)
+
+	stack := NewGitignoreStack(*sourceDir)
+
+	watcher, err := fsnotify.NewWatcher()
+	if err != nil {
+		logErrorf("watcher: %v", err)
+		os.Exit(1)
+	}
+	defer watcher.Close()
+
+	if err := addWatchersRecursively(watcher, *sourceDir, stack); err != nil {
+		logErrorf("watcher: %v", err)
+		os.Exit(1)
+	}
+
+	os.Remove(*socketPath)
+
+	ln, err := net.Listen("unix", *socketPath)
+	if err != nil {
+		logErrorf("socket: %v", err)
+		os.Exit(1)
+	}
+	defer func() {
+		ln.Close()
+		os.Remove(*socketPath)
+	}()
+
+	var mu sync.Mutex
+	debounceTimers := make(map[string]*time.Timer)
+	debounceOps := make(map[string]fsnotify.Op)
+
+	clients := make(map[net.Conn]bool)
+	var clientsMu sync.Mutex
+
+	go func() {
+		for {
+			conn, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			clientsMu.Lock()
+			clients[conn] = true
+			clientsMu.Unlock()
+			logDebug("client connected: %s", conn.RemoteAddr())
+
+			go func(c net.Conn) {
+				defer func() {
+					clientsMu.Lock()
+					delete(clients, c)
+					clientsMu.Unlock()
+					c.Close()
+				}()
+				buf := make([]byte, 1)
+				for {
+					if _, err := c.Read(buf); err != nil {
+						return
+					}
+				}
+			}(conn)
+		}
+	}()
+
+	broadcast := func(evt FileEvent) {
+		data, err := json.Marshal(evt)
+		if err != nil {
+			return
+		}
+		data = append(data, '\n')
+
+		clientsMu.Lock()
+		defer clientsMu.Unlock()
+		for c := range clients {
+			if _, err := c.Write(data); err != nil {
+				go func() {
+					clientsMu.Lock()
+					delete(clients, c)
+					clientsMu.Unlock()
+					c.Close()
+				}()
+			}
+		}
+	}
+
+	ctx, cancel := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer cancel()
+
+	go func() {
+		<-ctx.Done()
+		ln.Close()
+	}()
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+
+		case event, ok := <-watcher.Events:
+			if !ok {
+				return
+			}
+
+			relPath, err := filepath.Rel(*sourceDir, event.Name)
+			if err != nil {
+				continue
+			}
+
+			if isGitDir(relPath) {
+				continue
+			}
+
+			if stack.IsIgnored(relPath) {
+				continue
+			}
+
+			logDebug("event: %s %s", event.Op, relPath)
+
+			if event.Op&fsnotify.Create != 0 {
+				srcPath := filepath.Join(*sourceDir, relPath)
+				info, err := os.Lstat(srcPath)
+				if err == nil && info.IsDir() {
+					if hasGitignore(srcPath) {
+						stack.Push(srcPath)
+					}
+					if err := watcher.Add(srcPath); err != nil {
+						logErrorf("watch %s: %v", relPath, err)
+					}
+					filepath.Walk(srcPath, func(path string, info os.FileInfo, err error) error {
+						if err != nil || !info.IsDir() || path == srcPath {
+							return nil
+						}
+						watcher.Add(path)
+						return nil
+					})
+				}
+			}
+
+			mu.Lock()
+			if existing, exists := debounceOps[relPath]; exists {
+				debounceTimers[relPath].Stop()
+				debounceOps[relPath] = existing | event.Op
+			} else {
+				debounceOps[relPath] = event.Op
+			}
+			path := relPath
+			debounceTimers[relPath] = time.AfterFunc(200*time.Millisecond, func() {
+				mu.Lock()
+				op := debounceOps[path]
+				delete(debounceOps, path)
+				delete(debounceTimers, path)
+				mu.Unlock()
+
+				evt := FileEvent{Path: path}
+				switch {
+				case op&fsnotify.Create != 0:
+					evt.Op = "create"
+				case op&fsnotify.Write != 0:
+					evt.Op = "write"
+				case op&fsnotify.Remove != 0:
+					evt.Op = "remove"
+				case op&fsnotify.Rename != 0:
+					evt.Op = "remove"
+				default:
+					return
+				}
+
+				broadcast(evt)
+			})
+			mu.Unlock()
+
+		case err, ok := <-watcher.Errors:
+			if !ok {
+				return
+			}
+			logErrorf("watcher: %v", err)
+		}
+	}
+}
+
+func addWatchersRecursively(watcher *fsnotify.Watcher, root string, stack *GitignoreStack) error {
+	return filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		relPath, err := filepath.Rel(root, path)
+		if err != nil {
+			return err
+		}
+
+		if isGitDir(relPath) {
+			if info.IsDir() {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+
+		if info.IsDir() {
+			if hasGitignore(path) {
+				stack.Push(path)
+			}
+			if !stack.IsIgnored(relPath) {
+				return watcher.Add(path)
+			}
+		}
+
+		return nil
+	})
+}