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"
   },