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/acp/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/acp/README.md
-README.md: 3ba247598f29f2244456061fe7f9a3282086148f
-README.zh.md: c13bc05b12fff2ef97b4d547936aa14a6556430a
+README.md: 97af6d164b265bf0e98e3c9f5a444cffad4face5
+README.zh.md: 266b108c108b9f543d93cbb727ddbc01ab4bef36

packages/acp/README.md

@@ -2,10 +2,10 @@
 
 English | [中文](README.zh.md)
 
-The ACP group exposes harness agents to programmatic clients. It is an interoperability transport, not a presentation or human-interaction layer.
+The ACP group exposes harness agents to programmatic clients over the Agent Client Protocol. It is an interoperability transport, not a presentation or human-interaction layer; the matching out-of-process subagent *client* lives in [`subagent/subagent-acp`](../subagent/subagent-acp/README.md) because it implements the subagent provider interface.
 
 | Package | Role |
 |---|---|
 | [`acp/`](acp/README.md) | Automation-only ACP server. |
 
-The matching out-of-process subagent client remains in [`subagent/subagent-acp`](../subagent/subagent-acp/README.md) because it implements the subagent provider interface; arbitrary ACP clients may drive the same server contract.
+The server contract is documented in [`acp/README.md`](acp/README.md).

packages/acp/README.zh.md

@@ -2,10 +2,10 @@
 
 [English](README.md) | 中文
 
-ACP（Agent Client Protocol）组将 harness 中的 agent（智能体）公开给程序化客户端。它是互操作传输层，而非展示层或人机交互层。
+ACP 组通过 Agent Client Protocol 把 harness agent 暴露给编程客户端。它是互操作传输层，不是展示或人机交互层；配对的进程外 subagent *客户端*在 [`subagent/subagent-acp`](../subagent/subagent-acp/README.md)，因为它实现的是 subagent 提供方接口。
 
 | 包 | 职责 |
 |---|---|
 | [`acp/`](acp/README.md) | 仅面向自动化的 ACP 服务器。 |
 
-与之匹配的进程外 subagent 客户端仍位于 [`subagent/subagent-acp`](../subagent/subagent-acp/README.md)，因为它实现 subagent 提供方接口；任意 ACP 客户端都可以按照同一服务器契约驱动该服务器。
+服务器契约见 [`acp/README.md`](acp/README.md)。