More free models (#1244)

<!-- This is an auto-generated description by cubic. -->

## Summary by cubic
Adds support for free OpenRouter models and a new “Free (OpenRouter)”
auto option that fails over across free models for reliability. Improves
setup flow and UI with provider cards, a “Free” price badge, and an
OpenRouter setup prompt in chat.

- **New Features**
- Added OpenRouter free models: Qwen3 Coder (free), DeepSeek v3 (free),
DeepSeek v3.1 (free), marked with dollarSigns=0 and a “Free” badge.
- New auto model: “Free (OpenRouter)” that uses a fallback client to
cycle through free models with smart retry on transient errors.
- New SetupProviderCard component and updated SetupBanner with dedicated
Google and OpenRouter setup cards.
- Chat shows an OpenRouter setup prompt when “Free (OpenRouter)” is
selected and OpenRouter isn’t configured.
- New PriceBadge component in ModelPicker to display “Free” or price
tier.
- E2E: added setup flow test and option to show the setup screen in
tests.
- Model updates: added DeepSeek v3.1, updated Kimi K2 to kimi-k2-0905,
migrated providers to LanguageModelV2.

<!-- End of auto-generated description by cubic. -->

src/ipc/utils/llm_engine_provider.ts

@@ -1,4 +1,3 @@
-import { LanguageModel } from "ai";
 import { OpenAICompatibleChatLanguageModel } from "@ai-sdk/openai-compatible";
 import {
   FetchFunction,
@@ -9,6 +8,7 @@ import {
 import log from "electron-log";
 import { getExtraProviderOptions } from "./thinking_utils";
 import type { UserSettings } from "../../lib/schemas";
+import { LanguageModelV2 } from "@ai-sdk/provider";
 
 const logger = log.scope("llm_engine_provider");
 
@@ -53,7 +53,10 @@ export interface DyadEngineProvider {
   /**
 Creates a model for text generation.
 */
-  (modelId: ExampleChatModelId, settings?: ExampleChatSettings): LanguageModel;
+  (
+    modelId: ExampleChatModelId,
+    settings?: ExampleChatSettings,
+  ): LanguageModelV2;
 
   /**
 Creates a chat model for text generation.
@@ -61,7 +64,7 @@ Creates a chat model for text generation.
   chatModel(
     modelId: ExampleChatModelId,
     settings?: ExampleChatSettings,
-  ): LanguageModel;
+  ): LanguageModelV2;
 }
 
 export function createDyadEngine(