feat: add navigation and window size handlers with corresponding tests

internal/handlers/trackWindowSizeHandler.go

@@ -0,0 +1,21 @@
+package handlers
+
+import (
+	"github.com/StevanFreeborn/term-tier/internal/state"
+	tea "github.com/charmbracelet/bubbletea"
+)
+
+type trackWindowSizeHandler struct{}
+
+func NewTrackWindowSizeHandler() WinSizeMsgHandler {
+	return trackWindowSizeHandler{}
+}
+
+func (h trackWindowSizeHandler) Match(s state.State, msg tea.WindowSizeMsg) bool {
+	return true
+}
+
+func (h trackWindowSizeHandler) Handle(s state.State, msg tea.WindowSizeMsg) tea.Cmd {
+	s.SetWindowSize(msg.Width, msg.Height)
+	return nil
+}