docs: remove obsolete 普通 sub (old model) integration docs

The 普通 sub task-orchestration model was replaced by the template-agent model
and its backend deleted. Removed the now-obsolete docs describing it:
- heicode-desktop-sub-agile-api.md, heicode-desktop-subagile-e2e-demo.md
- heicode-desktop-unified-api.md, heicode-sub-mode-flow-spec.md
- 普通sub敏捷模式-AgentManager对接任务清单.md
- AgentManager普通sub{产物回调缺失问题,剩余补充要求,联调整改要求}.md

Fixed dangling references in the new docs (client-api / template-agent-model).
Swarm (蜂群) docs kept — different mode, out of scope.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/integration/heicode-desktop-client-api.md

@@ -5,7 +5,7 @@
 > 生产地址：`https://code.xinghanlab.com`
 > 状态图例：🟢 已实现并生产验证 · 🔴 待建（依赖 AM）
 
-> **本文取代旧的 `heicode-desktop-unified-api.md`**（那份描述的是已下线的 sub 任务编排模型：tasks/workflow/display_status/git_ref/产物下载等，均已删除）。新客户端一律按本文对接。
+> **本文取代旧的桌面 sub 任务编排接口文档**（描述 tasks/workflow/display_status/git_ref/产物下载的那套已下线，相关 md 已删除）。新客户端一律按本文对接。
 
 ---