fix: 修正 logo 中 N 和 G 字母造型

N 添加对角线笔画（█▄ █），G 添加内横杠（█ ▀█），
避免与 O 字母造型雷同。同步更新 ui.ts 中的硬编码 wordmark。

packages/core/test/session-compaction.test.ts

@@ -0,0 +1,18 @@
+import { expect, test } from "bun:test"
+import { SessionCompaction } from "@opencode-ai/core/session/compaction"
+
+test("compaction describes tool media without embedding base64", () => {
+  const base64 = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAAB"
+  const serialized = SessionCompaction.serializeToolContent([
+    { type: "text", text: "Image read successfully" },
+    {
+      type: "file",
+      uri: `data:image/png;base64,${base64}`,
+      mime: "image/png",
+      name: "pixel.png",
+    },
+  ])
+
+  expect(serialized).toBe("Image read successfully\n[Attached image/png: pixel.png]")
+  expect(serialized).not.toContain(base64)
+})