refactor(ai-toolbar): stack attachment previews by row

tests/ai-toolbar.test.ts

@@ -184,6 +184,13 @@ describe("AI capture redesign", () => {
 
 		expect(source).toContain("rounded-[10px] bg-card p-3 shadow-sm");
 	});
+
+	test("attachment previews stack one per row instead of using a two-column desktop grid", () => {
+		const source = readToolbarSource();
+
+		expect(source).not.toContain('"mt-3 grid gap-2 grid-cols-2"');
+		expect(source).toContain('"mt-3 grid gap-2"');
+	});
 });
 
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