docs: anchor each subsystem page to its package group; make group READMEs thin tables

core.md read as a type grab-bag: LLM wire vocabulary up front, the agent/loop story buried, and no correspondence to packages/core. It now opens on the packages/core control spine — the package-by-package loop map with a Page column into session/system-prompt/tools/scope — and keeps only what the spine group declares plus the repo-wide patterns: the Agent handle with its delivery/cancellation/interception contracts, the SessionEvent envelope, branded ids, the …Map pattern. The conversation vocabulary (Message/ContentBlock, the model request, adapters — 17 type-equiv blocks) moves to llm-streaming.md, which now declares packages/llm end-to-end; the duplicate ContentBlockMap paste near its seam section folds into the moved section, and the manifest, LINK_MAP, README table rows, website label (Core data structures → Core), and inbound anchors follow.

Every packages/<group>/README pair is now a thin front door in one shape: a why-first intro (bash's seam-pattern-first paragraph rewritten as 'shell execution for the agent'), the package table, and a closing pointer to the owning docs/subsystems page — the bash-style table stays the load-bearing middle. Load-bearing trailing paragraphs relocate rather than vanish: the fs no-timeout rationale becomes a filesystem.md section (both languages), session's four sectioned tables merge into one 12-row table, examples' legacy-bin H2 collapses to a pointer at jsonrpc-demo's README, and design rationale that already lives in an Agent Note or subsystem page is now linked instead of restated. All 40 pair records re-recorded.

packages/fs/README.zh.md

@@ -19,3 +19,5 @@
 ## 文件 I/O 不设超时
 
 `read`/`write`/`edit` **不** 接受 `timeoutMs`，提供方 seam 也不启动 deadline。这与 bash 和 web（两者使用 [`@deepseek-ai/dsh-timeout`](../util/timeout/README.md)）及基于 bash 的 `glob`/`grep` 不同（它们声明的 `timeoutMs` 由 `@deepseek-ai/dsh-timeout-policy` 强制执行）：这些工作由进程支持，deadline 可以实际终止工作。本地系统调用至多只能尽力中止：超时无法强制正在进行的 `fsync`/`rename` 停止，因此这里的 deadline 会成为无法兑现承诺的配置项。在此添加 deadline 还会在「显式优于隐式」明确禁止的地方引入隐式默认值。两个参考 agent（Claude Code、Codex）出于同一原因都不为文件 I/O 计时；取消仍通过工具执行信号传播，在系统调用边界尽力中止。
+
+子系统参考——目标、结果、防护、策略事件、错误分类体系，以及文件 IO 为何不设超时——见 [docs/subsystems/filesystem.md](../../docs/subsystems/filesystem.md)；沙箱围栏见[跨家族 fs 沙箱 Agent Note](../../.agents/notes/implemented/feature/2026-07-14-cross-family-fs-sandbox.md)。