test(ralph-loop): remove unsafe fixture assertions

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/ralph-loop/completion-promise-detector-test-input.test.ts

@@ -0,0 +1,23 @@
+/// <reference types="bun-types" />
+import type { PluginInput } from "@opencode-ai/plugin"
+
+export type SessionMessage = {
+	info?: { role?: string }
+	parts?: Array<{ type: string; text?: string }>
+}
+
+export function createPluginInput(messages: SessionMessage[]): PluginInput {
+	const pluginInput = {
+		client: { session: {} } as PluginInput["client"],
+		project: {} as PluginInput["project"],
+		directory: "/tmp",
+		worktree: "/tmp",
+		serverUrl: new URL("http://localhost"),
+		$: {} as PluginInput["$"],
+	} as PluginInput
+
+	const messagesFunction = testCoerce<PluginInput["client"]["session"]["messages"]>(async () => ({ data: messages }))
+	pluginInput.client.session.messages = messagesFunction
+
+	return pluginInput
+}