refactor: move config dir to ~/.config/hy3d, replace skill with run-hy3d

- config dir renamed hunyuan3dweb -> hy3d (cookies/profile moved intact,
  auth re-verified: quota 20/20)
- cli.py/login.py/READMEs/doc paths updated to ~/.config/hy3d
- skill: delete run-hunyuan3dweb, add run-hy3d pointing at bin/hy3d
- zero stale old-name references remain (one historical note in skill)

README.md

@@ -27,7 +27,7 @@ PYTHONPATH=$PWD python3 -m hy3d.cli quota
 ```bash
 hy3d auth login
 # → 按提示: 输邮箱 → 收验证码 → 输验证码
-# → cookie 自动保存到 ~/.config/hunyuan3dweb/cookies.txt
+# → cookie 自动保存到 ~/.config/hy3d/cookies.txt
 ```
 
 验证登录与配额：
@@ -141,8 +141,8 @@ CLI 等价写法：`hy3d --cookies /path/to/cookies.txt quota`，或环境变量
 
 ## 配置文件与目录
 
-- cookie：`~/.config/hunyuan3dweb/cookies.txt`（路径保持不变，避免重新登录）
-- 浏览器 profile：`~/.config/hunyuan3dweb/profile`
+- cookie：`~/.config/hy3d/cookies.txt`（全新目录，cookie 已随搬迁保留）
+- 浏览器 profile：`~/.config/hy3d/profile`
 - 环境变量：`HY3D_COOKIES`（cookie 路径）、`HY3D_JSON=1`（等同 `--json`）
 
 ## 文件结构