fix(session): cancel subtask child sessions (#25798)

packages/opencode/src/session/prompt.ts

@@ -1,6 +1,5 @@
 import path from "path"
 import os from "os"
-import z from "zod"
 import * as EffectZod from "@/util/effect-zod"
 import { SessionID, MessageID, PartID } from "./schema"
 import { MessageV2 } from "./message-v2"
@@ -121,9 +120,8 @@ export const layer = Layer.effect(
       return yield* EffectBridge.make()
     })
     const ops = Effect.fn("SessionPrompt.ops")(function* () {
-      const run = yield* runner()
       return {
-        cancel: (sessionID: SessionID) => run.fork(cancel(sessionID)),
+        cancel: (sessionID: SessionID) => cancel(sessionID),
         resolvePromptParts: (template: string) => resolvePromptParts(template),
         prompt: (input: PromptInput) => prompt(input),
       } satisfies TaskPromptOps