fix(web): repair merge tails — todo-row selector and composer handler clone

The #921 selector change and the duplication gate both first ran against
this branch after the merge made it MERGEABLE: assembly-surfaces still
queried the retired data-sample="todo-row" hook (the composed TodoRow
carries ToolRow's data-tool attribute instead), and the redesigned
QuestionComposer duplicated the custom-draft onChange/onKeyDown pair
across its inline input and optionless textarea. The spec now anchors on
data-tool="todo_write", and the composer shares one draftCustom /
continueFromCustom handler pair (Enter continues, Shift+Enter stays a
newline, IME composition stays inert).

packages/client/ui-conversation/tests/assembly-surfaces.spec.tsx

@@ -97,7 +97,7 @@ describe('todo_write assembly (product registrations, no outlet twins)', () => {
     const view = runtime.renderRoot()
 
     // Keyed toolview registration took the row (summary derived from args).
-    const row = view.container.querySelector('[data-sample="todo-row"]')
+    const row = view.container.querySelector('[data-tool="todo_write"]')
     expect(row).not.toBeNull()
     expect(row!.textContent).toContain('1/3 已完成 · 实现 fixture 样本')
 
@@ -117,7 +117,7 @@ describe('todo_write assembly (product registrations, no outlet twins)', () => {
     await waitFor(() => {
       expect(view.container.querySelector('[data-testid="todo-panel"]')).toBeNull()
     })
-    expect(view.container.querySelector('[data-sample="todo-row"]')).not.toBeNull()
+    expect(view.container.querySelector('[data-tool="todo_write"]')).not.toBeNull()
     await runtime.dispose()
   })
 })