Remove budget saver mode (#378)

This code was quite complex and hairy and resulted in very opaque errors
(for both free and pro users). There's not much benefit to budget saver
because Google removed 2.5 Pro free quota a while ago (after it
graduated the model from experimental to preview). Dyad Pro users can
still use 2.5 Flash free quota by disabling Dyad Pro by clicking on the
Dyad Pro button at the top.

src/main/llm_error_store.ts

@@ -1,35 +0,0 @@
-class LlmErrorStore {
-  private modelErrorToTimestamp: Record<string, number> = {};
-
-  constructor() {}
-
-  recordModelError({ model, provider }: { model: string; provider: string }) {
-    this.modelErrorToTimestamp[this.getKey({ model, provider })] = Date.now();
-  }
-
-  clearModelError({ model, provider }: { model: string; provider: string }) {
-    delete this.modelErrorToTimestamp[this.getKey({ model, provider })];
-  }
-
-  modelHasNoRecentError({
-    model,
-    provider,
-  }: {
-    model: string;
-    provider: string;
-  }): boolean {
-    const key = this.getKey({ model, provider });
-    const timestamp = this.modelErrorToTimestamp[key];
-    if (!timestamp) {
-      return true;
-    }
-    const oneHourAgo = Date.now() - 1000 * 60 * 60;
-    return timestamp < oneHourAgo;
-  }
-
-  private getKey({ model, provider }: { model: string; provider: string }) {
-    return `${provider}::${model}`;
-  }
-}
-
-export const llmErrorStore = new LlmErrorStore();