feat(cli-tools): add Grok Build setup

Add Grok Build to Dashboard → CLI Tools. Apply writes a [model.9router]
custom model to ~/.grok/config.toml and sets [models].default, routing
the xAI Grok TUI through 9Router. Reset removes the slot and restores
the previous default.

src/shared/constants/cliTools.js

@@ -363,6 +363,30 @@ amp --model "{{model}}"
       { id: "gemini-3.1-pro", name: "Gemini 3.1 Pro", alias: "gemini", defaultValue: "gemini/gemini-3.1-pro" },
     ],
   },
+  "grok-build": {
+    id: "grok-build",
+    name: "Grok Build",
+    image: "/providers/grok-cli.png",
+    color: "#1DA1F2",
+    description: "xAI Grok Build TUI coding agent",
+    configType: "custom",
+    docsUrl: "https://x.ai/cli",
+    defaultCommand: "grok",
+    notes: [
+      {
+        type: "info",
+        text: "Grok Build uses ~/.grok/config.toml. 9Router writes a [model.9router] custom model and sets it as the default.",
+      },
+      {
+        type: "info",
+        text: "After Apply, run grok (or /model 9router) to use the routed model. Switch back anytime with /model grok-build.",
+      },
+      {
+        type: "warning",
+        text: "Config path: Linux/macOS ~/.grok/config.toml • Windows %USERPROFILE%\\.grok\\config.toml",
+      },
+    ],
+  },
   // HIDDEN: gemini-cli
   // "gemini-cli": {
   //   id: "gemini-cli",