feat(app): add composer add menu with draft-preserving commands (#35711)

packages/app/test-browser/prompt-transient-state.test.ts

@@ -8,6 +8,8 @@ test("resets transient prompt input state when the prompt session changes", () =
     const [state, setState] = createPromptInputTransientState(identity, 3)
     setState({
       popover: "slash",
+      slashMenu: true,
+      slashMenuQuery: "compact",
       historyIndex: 2,
       savedPrompt: {
         prompt: [{ type: "text", content: "draft-A", start: 0, end: 7 }],
@@ -23,6 +25,8 @@ test("resets transient prompt input state when the prompt session changes", () =
 
     expect(state).toMatchObject({
       popover: null,
+      slashMenu: false,
+      slashMenuQuery: "",
       historyIndex: -1,
       savedPrompt: null,
       placeholder: 3,