Refactor observability configuration and support files

- Introduced `filterCertificateSupportFiles` function to filter support files for certificates in `agent.go`.
- Updated placeholder constants in `config_version.go` to reflect changes from support directory to certificate directory.
- Modified tests in `https_phase1_test.go` to align with new directory structure and removed obsolete checks for observability Lua scripts.
- Removed observability assets from `openresty_observability_assets.go` and created a new file `observability_assets.go` in `atsf_agent/internal/nginx` to manage observability Lua scripts.
- Updated documentation to reflect changes in configuration paths for certificates and Lua scripts.
- Ensured that the agent writes to the new `cert_dir` and `lua_dir` instead of the old `support_dir`.

README.md

@@ -215,7 +215,8 @@ Docker 镜像工作流仅构建 `atsf_server`，并产出 `linux/amd64` 与 `lin
 | `agent_token` | 节点专属认证 Token |
 | `discovery_token` | 首次自动注册使用的全局 Token |
 | `data_dir` | Agent 托管数据目录 |
-| `support_dir` | Agent 存放受管附属文件的目录，当前包含证书与 Lua 观测脚本 |
+| `cert_dir` | Agent 存放受管证书文件的目录 |
+| `lua_dir` | Agent 存放受管 Lua 观测脚本的目录；启动时自动覆盖释放 |
 | `openresty_observability_port` | Agent 读取 OpenResty Lua 本地观测指标的 loopback 端口 |
 | `observability_buffer_path` | Agent 本地观测补报缓冲文件路径 |
 | `observability_replay_minutes` | Agent 恢复 heartbeat 后允许自动补传的最近观测窗口分钟数 |