Add Gemini 3.1 Pro support and set Gemini default model (#11608)

Add Gemini 3.1 model entries for Gemini and Vertex providers.

Include the Gemini custom-tools endpoint model id in Gemini provider.
Update geminiDefaultModelId to gemini-3.1-pro-preview.

References:
- https://ai.google.dev/gemini-api/docs/models/gemini-3.1-pro-preview
- https://ai.google.dev/gemini-api/docs/pricing
- https://ai.google.dev/gemini-api/docs/thinking
- https://cloud.google.com/vertex-ai/generative-ai/docs/models/gemini/3-1-pro
- https://cloud.google.com/vertex-ai/generative-ai/pricing
- https://cloud.google.com/blog/products/ai-machine-learning/gemini-3-1-pro-on-gemini-cli-gemini-enterprise-and-vertex-ai
- https://deepmind.google/models/model-cards/gemini-3-1-pro/
- https://blog.google/innovation-and-ai/models-and-research/gemini-models/gemini-3-1-pro/

Author: PeterDaveHello

packages/types/src/providers/gemini.ts

@@ -3,9 +3,67 @@ import type { ModelInfo } from "../model.js"
 // https://ai.google.dev/gemini-api/docs/models/gemini
 export type GeminiModelId = keyof typeof geminiModels
 
-export const geminiDefaultModelId: GeminiModelId = "gemini-3-pro-preview"
+export const geminiDefaultModelId: GeminiModelId = "gemini-3.1-pro-preview"
 
 export const geminiModels = {
+	"gemini-3.1-pro-preview": {
+		maxTokens: 65_536,
+		contextWindow: 1_048_576,
+		supportsImages: true,
+		supportsPromptCache: true,
+		supportsReasoningEffort: ["low", "medium", "high"],
+		reasoningEffort: "low",
+
+		supportsTemperature: true,
+		defaultTemperature: 1,
+		inputPrice: 4.0,
+		outputPrice: 18.0,
+		cacheReadsPrice: 0.4,
+		cacheWritesPrice: 4.5,
+		tiers: [
+			{
+				contextWindow: 200_000,
+				inputPrice: 2.0,
+				outputPrice: 12.0,
+				cacheReadsPrice: 0.2,
+			},
+			{
+				contextWindow: Infinity,
+				inputPrice: 4.0,
+				outputPrice: 18.0,
+				cacheReadsPrice: 0.4,
+			},
+		],
+	},
+	"gemini-3.1-pro-preview-customtools": {
+		maxTokens: 65_536,
+		contextWindow: 1_048_576,
+		supportsImages: true,
+		supportsPromptCache: true,
+		supportsReasoningEffort: ["low", "medium", "high"],
+		reasoningEffort: "low",
+
+		supportsTemperature: true,
+		defaultTemperature: 1,
+		inputPrice: 4.0,
+		outputPrice: 18.0,
+		cacheReadsPrice: 0.4,
+		cacheWritesPrice: 4.5,
+		tiers: [
+			{
+				contextWindow: 200_000,
+				inputPrice: 2.0,
+				outputPrice: 12.0,
+				cacheReadsPrice: 0.2,
+			},
+			{
+				contextWindow: Infinity,
+				inputPrice: 4.0,
+				outputPrice: 18.0,
+				cacheReadsPrice: 0.4,
+			},
+		],
+	},
 	"gemini-3-pro-preview": {
 		maxTokens: 65_536,
 		contextWindow: 1_048_576,

packages/types/src/providers/vertex.ts

@@ -6,6 +6,35 @@ export type VertexModelId = keyof typeof vertexModels
 export const vertexDefaultModelId: VertexModelId = "claude-sonnet-4-5@20250929"
 
 export const vertexModels = {
+	"gemini-3.1-pro-preview": {
+		maxTokens: 65_536,
+		contextWindow: 1_048_576,
+		supportsImages: true,
+		supportsPromptCache: true,
+		supportsReasoningEffort: ["low", "medium", "high"],
+		reasoningEffort: "low",
+
+		supportsTemperature: true,
+		defaultTemperature: 1,
+		inputPrice: 4.0,
+		outputPrice: 18.0,
+		cacheReadsPrice: 0.4,
+		cacheWritesPrice: 4.5,
+		tiers: [
+			{
+				contextWindow: 200_000,
+				inputPrice: 2.0,
+				outputPrice: 12.0,
+				cacheReadsPrice: 0.2,
+			},
+			{
+				contextWindow: Infinity,
+				inputPrice: 4.0,
+				outputPrice: 18.0,
+				cacheReadsPrice: 0.4,
+			},
+		],
+	},
 	"gemini-3-pro-preview": {
 		maxTokens: 65_536,
 		contextWindow: 1_048_576,