实现服务启动时自动生成OpenAPI文档

主要变更:
1. 新增 cmd/api/docs.go 实现文档自动生成逻辑
2. 修改 cmd/api/main.go 在服务启动时调用文档生成
3. 重构 cmd/gendocs/main.go 提取生成函数
4. 更新 .gitignore 忽略自动生成的 openapi.yaml
5. 新增 Makefile 支持 make docs 命令
6. OpenSpec 框架更新和变更归档

功能特性:
- 服务启动时自动生成 OpenAPI 文档到项目根目录
- 保留独立的文档生成工具 (make docs)
- 生成失败时记录错误但不影响服务启动
- 所有代码已通过 openspec validate --strict 验证

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.claude/commands/openspec/proposal.md

@@ -10,6 +10,7 @@ tags: [openspec, change]
 - Keep changes tightly scoped to the requested outcome.
 - Refer to `openspec/AGENTS.md` (located inside the `openspec/` directory—run `ls openspec` or `openspec update` if you don't see it) if you need additional OpenSpec conventions or clarifications.
 - Identify any vague or ambiguous details and ask the necessary follow-up questions before editing files.
+- Do not write any code during the proposal stage. Only create design documents (proposal.md, tasks.md, design.md, and spec deltas). Implementation happens in the apply stage after approval.
 
 **Steps**
 1. Review `openspec/project.md`, run `openspec list` and `openspec list --specs`, and inspect related code or docs (e.g., via `rg`/`ls`) to ground the proposal in current behaviour; note any gaps that require clarification.