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/agents/dynamic-agent-prompt-builder.test.ts

@@ -181,7 +181,7 @@ describe("buildParallelDelegationSection", () => {
 
   it("#given non-Claude model with deep category #when building #then returns aggressive delegation section", () => {
     //#given
-    const model = "google/gemini-3-pro"
+    const model = "google/gemini-3.1-pro"
     const categories = [deepCategory, otherCategory]
 
     //#when
@@ -237,7 +237,7 @@ describe("buildParallelDelegationSection", () => {
 describe("buildNonClaudePlannerSection", () => {
   it("#given non-Claude model #when building #then returns plan agent section", () => {
     //#given
-    const model = "google/gemini-3-pro"
+    const model = "google/gemini-3.1-pro"
 
     //#when
     const result = buildNonClaudePlannerSection(model)
@@ -272,4 +272,3 @@ describe("buildNonClaudePlannerSection", () => {
   })
 })
 
-