feat: improve tmux session management and UX

Replace hardcoded setTimeout timing with exec channel polling for
reliable tmux session readiness detection. Add meaningful session
naming (termix-<hostId>-<rand>), aggressive-resize for multi-client
support, and a detach button in the terminal UI.

src/ui/locales/en.json

@@ -1872,6 +1872,8 @@
     "tmuxTimeDays": "{{count}}d ago",
     "tmuxCreateNew": "Start new session",
     "tmuxCopyHint": "Adjust selection and press Enter to copy to clipboard",
+    "tmuxDetach": "Detach from tmux session",
+    "tmuxDetached": "Detached from tmux session",
     "maxReconnectAttemptsReached": "Maximum reconnection attempts reached",
     "connectionLost": "Connection lost",
     "reconnect": "Reconnect",

src/ui/locales/translated/zh_CN.json

@@ -1586,6 +1586,8 @@
     "tmuxTimeDays": "{{count}}d ago",
     "tmuxCreateNew": "开始新会话",
     "tmuxCopyHint": "调整选区并按回车键复制到剪贴板",
+    "tmuxDetach": "从 tmux 会话分离",
+    "tmuxDetached": "已从 tmux 会话分离",
     "maxReconnectAttemptsReached": "已达到最大重连尝试次数",
     "closeTab": "关闭",
     "connectionTimeout": "连接超时",