feat(waiter): Bubble Tea TUI modernization

Replace the line-based REPL with a full-screen Bubble Tea TUI in
interactive mode (non-TTY still falls back to the line editor).

Layout (deveco-code inspired, no emoji):
  - Top status bar: HomeAgent brand + connection dot + mode + addr
  - Scrollable chat viewport with role-based rendering:
      You (purple)   user messages
      小宅 (orange)  agent responses
      · reasoning    dim gray italic, streaming-merged
      [ok]/[fail]    tool calls with status + truncated result
      [sys]          builtin command output
      [err]          errors
  - Rounded-border input box with placeholder
  - Bottom status bar: spinner while busy / hints + connection state

Key design points:
  - reader generation counter prevents stale errors from the old
    reader being mistaken for the new one after reconnect
  - handleSubmit always returns waitServer when reader is alive,
    so server responses to builtin commands like /status are received
  - History stored as *History (was copying sync.Mutex by value)
  - Chinese CJK wide-char aware word wrap with hanging indent
  - /clear /exit /quit handled in TUI; other /cmds still go through
    handleBuiltin with output captured to message area

Verified via tmux PTY: /help, /status, /clear, real chat with LLM
(reasoning -> tool_call -> response chain all render correctly).

cmd/waiter/history.go

@@ -13,8 +13,8 @@ type History struct {
 	mu    sync.Mutex
 }
 
-func newHistory(path string, max int) History {
-	return History{path: path, max: max}
+func newHistory(path string, max int) *History {
+	return &History{path: path, max: max}
 }
 
 func (h *History) load() {