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/subagent/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/subagent/README.md
-README.md: 0a342569e66539e4987710b2e56f2946c97b1ac1
-README.zh.md: 5d2f7beef478b8bfd27b4772c7a951ea62cb10ef
+README.md: c8969ad313fc673456d2740b40d90c6d8db794ac
+README.zh.md: fb18afba5d8680408f0f37ab75056a3fb0ef660a

packages/subagent/README.md

@@ -19,3 +19,5 @@ This family lets an agent delegate work to child agents. Multiple named provider
 | [`tool-subagent-report/`](tool-subagent-report/README.md) | Provides the child-to-parent report channel | registers in child scopes |
 
 See the decisions for the [capability family](../../.agents/notes/implemented/feature/2026-06-21-subagent-capability-seam.md), [continuable children](../../.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.md), and [control tools](../../.agents/notes/implemented/simplification/2026-07-26-merge-subagent-control-service.md).
+
+The subsystem reference — start requests, results, live runs, the provider seam, continuable background children — is [docs/subsystems/subagent.md](../../docs/subsystems/subagent.md); design rationale in the [subagent capability seam](../../.agents/notes/implemented/feature/2026-06-21-subagent-capability-seam.md), [continuable background subagents](../../.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.md), and [merged subagent control service](../../.agents/notes/implemented/simplification/2026-07-26-merge-subagent-control-service.md) Agent Notes.

packages/subagent/README.zh.md

@@ -19,3 +19,5 @@
 | [`tool-subagent-report/`](tool-subagent-report/README.md) | 提供从子级到父级的报告通道 | 注册到子级作用域 |
 
 参见[能力家族](../../.agents/notes/implemented/feature/2026-06-21-subagent-capability-seam.md)、[可继续执行的子级](../../.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.md)和[控制工具](../../.agents/notes/implemented/simplification/2026-07-26-merge-subagent-control-service.md)决策。
+
+子系统参考——启动请求、结果、实时运行、提供方 seam、可续跑后台子 agent——见 [docs/subsystems/subagent.md](../../docs/subsystems/subagent.md)；设计依据见 [subagent 能力 seam](../../.agents/notes/implemented/feature/2026-06-21-subagent-capability-seam.md)、[可续跑后台 subagent](../../.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.md) 与[合并 subagent 控制服务](../../.agents/notes/implemented/simplification/2026-07-26-merge-subagent-control-service.md) Agent Note。