fix(delegate-task): resolve variant-bearing fallback models during immediate selection

🤖 Generated with [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-openagent)

src/tools/delegate-task/model-selection.test.ts

@@ -1,5 +1,4 @@
-declare const require: (name: string) => any
-const { describe, test, expect, beforeEach, afterEach, spyOn, mock } = require("bun:test")
+import { afterEach, beforeEach, describe, expect, mock, spyOn, test } from "bun:test"
 import { resolveModelForDelegateTask } from "./model-selection"
 import * as connectedProvidersCache from "../../shared/connected-providers-cache"
 
@@ -105,6 +104,26 @@ describe("resolveModelForDelegateTask", () => {
 				expect(result!.model).toBe("anthropic/claude-sonnet-4-6")
 			})
 		})
+
+		describe("#when user fallback models include variant syntax", () => {
+			test("#then resolves a parenthesized variant against the base available model", () => {
+				const result = resolveModelForDelegateTask({
+					userFallbackModels: ["openai/gpt-5.2(high)"],
+					availableModels: new Set(["openai/gpt-5.2"]),
+				})
+
+				expect(result).toEqual({ model: "openai/gpt-5.2", variant: "high" })
+			})
+
+			test("#then resolves a space-separated variant against the base available model", () => {
+				const result = resolveModelForDelegateTask({
+					userFallbackModels: ["gpt-5.2 medium"],
+					availableModels: new Set(["openai/gpt-5.2"]),
+				})
+
+				expect(result).toEqual({ model: "openai/gpt-5.2", variant: "medium" })
+			})
+		})
 	})
 
 	describe("#given only connected providers cache exists (no provider-models cache)", () => {