tui: improve plan mode switching and question handling

- Add automatic agent switching when plan tools complete
- Add custom option control to question interface
- Update plan tool descriptions to clarify agent switching
- Show plan file path in exit/exit prompts
- Remove custom answer option when not needed

packages/sdk/js/src/v2/gen/types.gen.ts

@@ -545,6 +545,10 @@ export type QuestionInfo = {
    * Allow selecting multiple choices
    */
   multiple?: boolean
+  /**
+   * Allow typing a custom answer (default: true)
+   */
+  custom?: boolean
 }
 
 export type QuestionRequest = {
@@ -706,6 +710,7 @@ export type PermissionRuleset = Array<PermissionRule>
 
 export type Session = {
   id: string
+  slug: string
   projectID: string
   directory: string
   parentID?: string