fix(models): remove stale Gemini 3 Pro references

Keep repo-owned CLI, docs, and test fixtures aligned with current Gemini 3.1 naming while leaving upstream catalog behavior untouched.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/cli/tui-install-prompts.ts

@@ -54,7 +54,7 @@ export async function promptInstallConfig(detected: DetectedConfig): Promise<Ins
     message: "Will you integrate Google Gemini?",
     options: [
       { value: "no", label: "No", hint: "Frontend/docs agents will use fallback" },
-      { value: "yes", label: "Yes", hint: "Beautiful UI generation with Gemini 3 Pro" },
+      { value: "yes", label: "Yes", hint: "Beautiful UI generation with Gemini 3.1 Pro" },
     ],
     initialValue: initial.gemini,
   })