refactor: remove broken ask tool in favor of askquestion

The ask tool used Bus events that never reached the tool's subscription
due to Instance.state scoping issues. The askquestion tool (upstream PR
anomalyco#5958) uses HTTP endpoints and works correctly.

Removed:
- ask tool registration and implementation
- Question namespace schemas
- DialogQuestion UI components
- TuiEvent.QuestionRequest/Response event types
- ask.test.ts tests

Updated plan.txt to reference askquestion instead of ask.

Author: shuv1337

packages/opencode/src/cli/cmd/tui/app.tsx

@@ -31,8 +31,6 @@ import { ToastProvider, useToast } from "./ui/toast"
 import { ExitProvider, useExit } from "./context/exit"
 import { Session as SessionApi } from "@/session"
 import { TuiEvent } from "./event"
-import { DialogQuestion } from "@tui/component/dialog-question"
-import type { Question } from "@/question"
 import { KVProvider, useKV } from "./context/kv"
 import { Provider } from "@/provider/provider"
 import { ArgsProvider, useArgs, type Args } from "./context/args"
@@ -547,55 +545,6 @@ function App() {
     })
   })
 
-  // Handle question requests from the Ask tool
-  sdk.event.on(TuiEvent.QuestionRequest.type as any, (evt: any) => {
-    const request = evt.properties as Question.Request
-    dialog.replace(
-      () => (
-        <DialogQuestion
-          request={request}
-          onSubmit={(answers) => {
-            sdk.client.tui.publish({
-              body: {
-                type: TuiEvent.QuestionResponse.type,
-                properties: {
-                  questionID: request.questionID,
-                  status: "ok",
-                  answers,
-                },
-              },
-            } as any)
-          }}
-          onCancel={() => {
-            sdk.client.tui.publish({
-              body: {
-                type: TuiEvent.QuestionResponse.type,
-                properties: {
-                  questionID: request.questionID,
-                  status: "cancel",
-                  answers: [],
-                },
-              },
-            } as any)
-          }}
-        />
-      ),
-      () => {
-        // On escape/close, send cancel response
-        sdk.client.tui.publish({
-          body: {
-            type: TuiEvent.QuestionResponse.type,
-            properties: {
-              questionID: request.questionID,
-              status: "cancel",
-              answers: [],
-            },
-          },
-        } as any)
-      },
-    )
-  })
-
   sdk.event.on(SessionApi.Event.Deleted.type, (evt) => {
     if (route.data.type === "session" && route.data.sessionID === evt.properties.info.id) {
       route.navigate({ type: "home" })