refactor(terminal-dashboard): simplify CLI launch to dialog-only mode

- Replace dropdown menu with direct dialog button
- Remove unused state variables (selectedTool, launchMode, selectedShell)
- Update button icon to Plus and label to "New Session"
- Clean up i18n keys (remove unused tool/mode/shell options)

ccw/frontend/src/locales/en/terminal-dashboard.json

@@ -78,15 +78,8 @@
     "layoutSplitH": "Split Horizontal",
     "layoutSplitV": "Split Vertical",
     "layoutGrid": "Grid 2x2",
-    "launchCli": "Launch CLI",
-    "tool": "Tool",
-    "mode": "Mode",
-    "modeDefault": "Default",
-    "modeYolo": "Yolo",
-    "shell": "Shell",
-    "shellCmdDesc": "(Recommended for Windows)",
-    "quickCreate": "Quick Create",
-    "configure": "Configure...",
+    "launchCli": "New Session",
+    "launchCliHint": "Click to configure and create a new CLI session",
     "fullscreen": "Fullscreen",
     "orchestrator": "Orchestrator"
   },

ccw/frontend/src/locales/zh/terminal-dashboard.json

@@ -78,15 +78,8 @@
     "layoutSplitH": "左右分割",
     "layoutSplitV": "上下分割",
     "layoutGrid": "2x2 网格",
-    "launchCli": "启动 CLI",
-    "tool": "工具",
-    "mode": "模式",
-    "modeDefault": "默认",
-    "modeYolo": "Yolo",
-    "shell": "Shell",
-    "shellCmdDesc": "(推荐 Windows)",
-    "quickCreate": "快速创建",
-    "configure": "配置...",
+    "launchCli": "新建会话",
+    "launchCliHint": "点击配置并创建新的 CLI 会话",
     "fullscreen": "全屏",
     "orchestrator": "编排器"
   },