Add Windows-assisted initial sync for faster startup

New protocol:
- Windows binary scans directory (fast native NTFS) and sends manifest
- Container receives manifest, compares with local /data state
- Only copies files that differ (size, modtime, mode, symlink)

Protocol messages:
- manifest: sends full file metadata from Windows
- manifest_done: signals manifest transfer complete
- event_create/write/remove: file change events

Flow:
1. Container connects to socket
2. Windows binary sends manifest (file metadata)
3. Container scans /data (fast local volume)
4. Container copies only changed files from /host (9P bind mount)
5. Container enters event-waiting loop

This dramatically speeds up initial sync by avoiding slow 9P scans.

1 files changed, 137 insertions, 28 deletions

diff --git a/cmd_windows.go b/cmd_windows.go
index b68851a..61c7f1d 100644
--- a/cmd_windows.go
+++ b/cmd_windows.go
@@ -3,8 +3,8 @@
 package main
 
 import (
+	"bufio"
 	"context"
-	"encoding/json"
 	"flag"
 	"fmt"
 	"net"
@@ -38,10 +38,12 @@ func run() {
 	}
 	SetLogLevel(level)
 
-	logInfo("watcher: starting on %s", *sourceDir)
-	logInfo("watcher: serving on %s", *socketPath)
+	logInfo("watcher: scanning %s ...", *sourceDir)
 
 	stack := NewGitignoreStack(*sourceDir)
+	manifest := scanDirectory(*sourceDir, stack)
+
+	logInfo("watcher: found %d files, serving on %s", len(manifest.Files), *socketPath)
 
 	watcher, err := fsnotify.NewWatcher()
 	if err != nil {
@@ -86,40 +88,25 @@ func run() {
 			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
-					}
+				sendManifest(c, manifest)
+
+				scanner := bufio.NewScanner(c)
+				for scanner.Scan() {
 				}
+
+				clientsMu.Lock()
+				delete(clients, c)
+				clientsMu.Unlock()
+				c.Close()
 			}(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()
-				}()
-			}
+			sendEvent(c, evt)
 		}
 	}
 
@@ -205,6 +192,39 @@ func run() {
 					return
 				}
 
+				// Update manifest
+				srcPath := filepath.Join(*sourceDir, path)
+				switch evt.Op {
+				case "create":
+					if info, err := os.Lstat(srcPath); err == nil {
+						linkTarget := ""
+						if info.Mode()&os.ModeSymlink != 0 {
+							linkTarget, _ = os.Readlink(srcPath)
+						}
+						manifest.Files[path] = FileMeta{
+							Size:    info.Size(),
+							Mode:    info.Mode(),
+							ModTime: info.ModTime(),
+							Symlink: linkTarget,
+						}
+					}
+				case "write":
+					if info, err := os.Lstat(srcPath); err == nil {
+						linkTarget := ""
+						if info.Mode()&os.ModeSymlink != 0 {
+							linkTarget, _ = os.Readlink(srcPath)
+						}
+						manifest.Files[path] = FileMeta{
+							Size:    info.Size(),
+							Mode:    info.Mode(),
+							ModTime: info.ModTime(),
+							Symlink: linkTarget,
+						}
+					}
+				case "remove":
+					delete(manifest.Files, path)
+				}
+
 				broadcast(evt)
 			})
 			mu.Unlock()
@@ -218,6 +238,95 @@ func run() {
 	}
 }
 
+func scanDirectory(root string, stack *GitignoreStack) *Manifest {
+	manifest := &Manifest{Files: make(map[string]FileMeta)}
+
+	filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return nil
+		}
+
+		relPath, err := filepath.Rel(root, path)
+		if err != nil {
+			return nil
+		}
+
+		if relPath == "." {
+			return nil
+		}
+
+		if isGitDir(relPath) {
+			if info.IsDir() {
+				return filepath.SkipDir
+			}
+			return nil
+		}
+
+		if info.IsDir() && hasGitignore(path) {
+			stack.Push(path)
+		}
+
+		if stack.IsIgnored(relPath) {
+			return nil
+		}
+
+		linkTarget := ""
+		if info.Mode()&os.ModeSymlink != 0 {
+			linkTarget, _ = os.Readlink(path)
+		}
+
+		manifest.Files[relPath] = FileMeta{
+			Size:    info.Size(),
+			Mode:    info.Mode(),
+			ModTime: info.ModTime(),
+			Symlink: linkTarget,
+		}
+
+		return nil
+	})
+
+	return manifest
+}
+
+func sendManifest(conn net.Conn, manifest *Manifest) {
+	msg := &ProtocolMessage{
+		Type:  "manifest",
+		Files: manifest.ToJSON(),
+	}
+	data, err := EncodeMessage(msg)
+	if err != nil {
+		return
+	}
+	data = append(data, '\n')
+	conn.Write(data)
+
+	done := &ProtocolMessage{Type: "manifest_done"}
+	doneData, _ := EncodeMessage(done)
+	doneData = append(doneData, '\n')
+	conn.Write(doneData)
+}
+
+func sendEvent(conn net.Conn, evt FileEvent) {
+	msg := &ProtocolMessage{
+		Type: "event",
+		Path: evt.Path,
+	}
+	switch evt.Op {
+	case "create":
+		msg.Type = "event_create"
+	case "write":
+		msg.Type = "event_write"
+	case "remove":
+		msg.Type = "event_remove"
+	}
+	data, err := EncodeMessage(msg)
+	if err != nil {
+		return
+	}
+	data = append(data, '\n')
+	conn.Write(data)
+}
+
 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 {