Revert "fix: attach inline prompt to cell.inputArea (under the editor), not cell.node"

This reverts commit 8ed55c43c7.

src/__tests__/opencode_cell_actions.spec.ts

@@ -87,7 +87,6 @@ function makeFakeCell(
   const cell = new (CodeCell as unknown as new () => CodeCell)();
   (cell as any).model = model;
   (cell as any).node = document.createElement('div');
-  (cell as any).inputArea = { node: document.createElement('div') };
 
   const notebook: any = { widgets: [] as CodeCell[] };
   const panel: any = {
@@ -128,7 +127,7 @@ describe('OpenCodeCellActions', () => {
     const actions = new OpenCodeCellActions(cell);
     const btns = actions.node.querySelectorAll('button');
     expect(btns.length).toBe(1);
-    expect(btns[0].textContent).toContain('AI');
+    expect(btns[0].textContent).toContain('🪄');
   });
 
   it('disables the button when notebook panel cannot be resolved', () => {
@@ -155,7 +154,7 @@ describe('OpenCodeCellActions', () => {
     const btn = actions.node.querySelector('button') as HTMLButtonElement;
     btn.click();
 
-    const prompt = cell.inputArea!.node.querySelector(
+    const prompt = cell.node.querySelector(
       '.opencode-inline-prompt'
     ) as HTMLElement;
     expect(prompt).not.toBeNull();
@@ -170,7 +169,7 @@ describe('OpenCodeCellActions', () => {
     const btn = actions.node.querySelector('button') as HTMLButtonElement;
     btn.click();
     btn.click();
-    expect(cell.inputArea!.node.querySelector('.opencode-inline-prompt')).toBeNull();
+    expect(cell.node.querySelector('.opencode-inline-prompt')).toBeNull();
   });
 
   it('disconnects model signals on dispose', () => {
@@ -197,7 +196,7 @@ describe('OpenCodeCellActions', () => {
     const btn = actions.node.querySelector('button') as HTMLButtonElement;
     btn.click();
 
-    const select = cell.inputArea!.node.querySelector(
+    const select = cell.node.querySelector(
       '.opencode-inline-prompt .opencode-model-select'
     ) as HTMLSelectElement;
     expect(select).not.toBeNull();
@@ -220,7 +219,7 @@ describe('OpenCodeCellActions', () => {
     btn.click();
 
     expect(
-      cell.inputArea!.node.querySelector('.opencode-inline-prompt .opencode-model-select')
+      cell.node.querySelector('.opencode-inline-prompt .opencode-model-select')
     ).toBeNull();
   });
 });

src/components/opencode_cell_actions.ts

@@ -121,7 +121,7 @@ export class OpenCodeCellActions extends Widget {
         this._hidePrompt();
       }
     });
-    Widget.attach(prompt, this._cell.inputArea?.node ?? this._cell.node);
+    Widget.attach(prompt, this._cell.node);
     this._prompt = prompt;
   }