docs(readme): lead with the CRT tile grid animation

The hero GIF is now six live agents (DeepSeek Harness, Claude Code, Pi,
Codex, OpenCode, a shell) powering on and off in the tile grid, captured
frame-stepped at 60fps from a real instance. Replaces the July subagent
demo in both READMEs; the old GIF file stays in docs/images.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

README.zh-CN.md

@@ -28,7 +28,7 @@
 </p>
 
 <p align="center">
-  <img src="docs/images/subagent-demo-20260724.gif" alt="Codeman — 并行子智能体可视化" width="900">
+  <img src="docs/images/tiles-crt-20261010.gif" alt="Codeman 平铺视图：六个实时智能体（DeepSeek Harness、Claude Code、Pi、Codex、OpenCode 和一个 shell）以 CRT 动画开启与关闭" width="800">
 </p>
 
 > 本文档由英文版 [`README.md`](README.md) 翻译而来。如有出入，以英文版为准。