docs: give subsystems/ its own README index; retire the data-structures-catalog framing

core.md doubled as the folder index: its intro claimed "this folder catalogs the data structures" and carried the 38-row page table, wording that predates the one-page-per-subsystem shape where every page also carries its generated Cordis surface. The folder index now lives in docs/subsystems/README.md (page table plus the type-equiv note), and core.md is one subsystem page among siblings: the spine vocabulary. Structural referents move with it: the docs/AGENTS.md tier table and update rule, development.md's type-equiv pointer, the dsh-code-review skill, the two owning catalog Agent Notes, and website/docs.ts (README projects as reference/subsystems/index.md and takes the docs/subsystems folder alias; sidebar orders shift by one). Remaining "data-structure catalog" / "sub-page" phrasing in active notes and READMEs is reworded to subsystem-page terms in both languages; touched pairs re-recorded; translation-prompt snapshot re-recorded (its example embeds development.md).

packages/subprocess/subprocess/README.zh.md

@@ -15,7 +15,7 @@
 - `scrubbedParentEnv()` / `SENSITIVE_ENV_PATTERN` 是唯一一份共享的环境清理定义：环境中形似凭据的名称与 `DSH_*` 名称都会被丢弃，显式 `env` 在清除之后合并。本地的普通 spawn 与终端 spawn 都应用该定义；拥有自身 spawn 的 SDK 管理传输可直接导入它。
 - 服务自身的 dispose（资源释放）会终止所有仍在运行的受管进程并等待其退出。
 
-参见[子进程数据结构目录](../../../docs/subsystems/subprocess.md)与[seam Agent Note（agent 决策记录）](../../../.agents/notes/implemented/architecture/2026-07-26-subprocess-seam.md)。
+参见[子进程子系统页面](../../../docs/subsystems/subprocess.md)与[seam Agent Note（agent 决策记录）](../../../.agents/notes/implemented/architecture/2026-07-26-subprocess-seam.md)。
 
 ## 模型体验