fix: playlist title encoding via MultiByteToWideChar

Winamp IPC_GETPLAYLISTTITLE returns ANSI (char*) strings in its process
memory. Blindly casting bytes to string garbles umlauts and other non-ASCII
chars. Fix: decode via MultiByteToWideChar(CP_ACP) → UTF-16 → Go string,
using the same code page Windows uses for the title.

Also check ReadProcessMemory return value — failures now return empty
string instead of garbage.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/winamp/winamp.go

@@ -21,6 +21,7 @@ var (
 	getWindowThreadProcessId = user32.NewProc("GetWindowThreadProcessId")
 	openProcess              = kernel32.NewProc("OpenProcess")
 	readProcessMemory        = kernel32.NewProc("ReadProcessMemory")
+	multiByteToWideChar      = kernel32.NewProc("MultiByteToWideChar")
 )
 
 const (
@@ -238,26 +239,58 @@ type TrackInfo struct {
 	Title string `json:"title"`
 }
 
-// readRemoteString reads a null-terminated ANSI string from another process.
+// readRemoteString reads a null-terminated ANSI string from another process
+// and converts it to UTF-8 via MultiByteToWideChar (CP_ACP = 0) so that
+// umlauts and other non-ASCII characters are handled correctly regardless of
+// the active Windows code page.
 func readRemoteString(proc syscall.Handle, ptr uintptr) string {
 	if ptr == 0 {
 		return ""
 	}
 	buf := make([]byte, 512)
 	var read uintptr
-	readProcessMemory.Call(
+	ok, _, _ := readProcessMemory.Call(
 		uintptr(proc),
 		ptr,
 		uintptr(unsafe.Pointer(&buf[0])),
 		uintptr(len(buf)),
 		uintptr(unsafe.Pointer(&read)),
 	)
-	for i, b := range buf {
+	if ok == 0 || read == 0 {
+		return ""
+	}
+
+	// Trim to null terminator.
+	ansi := buf[:read]
+	for i, b := range ansi {
 		if b == 0 {
-			return string(buf[:i])
+			ansi = ansi[:i]
+			break
 		}
 	}
-	return string(buf)
+	if len(ansi) == 0 {
+		return ""
+	}
+
+	// First call: query required UTF-16 buffer size.
+	const cpACP = 0
+	n, _, _ := multiByteToWideChar.Call(
+		cpACP, 0,
+		uintptr(unsafe.Pointer(&ansi[0])), uintptr(len(ansi)),
+		0, 0,
+	)
+	if n == 0 {
+		return string(ansi) // fallback: treat as latin-1
+	}
+
+	// Second call: do the conversion.
+	wide := make([]uint16, n)
+	multiByteToWideChar.Call(
+		cpACP, 0,
+		uintptr(unsafe.Pointer(&ansi[0])), uintptr(len(ansi)),
+		uintptr(unsafe.Pointer(&wide[0])), n,
+	)
+	return syscall.UTF16ToString(wide)
 }
 
 // GetPlaylist returns all titles in the current Winamp playlist.