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/sandbox/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/sandbox/README.md
-README.md: 1ba56d22330c26302c9283b2319d983ebf902219
-README.zh.md: 5daf830854297fe14c6560dbcde8a380ad079a0e
+README.md: 61127118c895cce728ab0b4eed387f51054a83f1
+README.zh.md: 984a677aad6ab97579abf861ea8b99f149c07d08

packages/sandbox/README.md

@@ -11,3 +11,5 @@ This family applies per-session confinement policy to process execution. It cove
 | [`sandbox-policy/`](sandbox-policy/README.md) | Resolves durable per-session sandbox policy | `ctx.sandboxPolicy` |
 
 See the [sandbox decision](../../.agents/notes/implemented/feature/2026-07-06-sandbox.md) for the capability boundary and the [filesystem integration decision](../../.agents/notes/implemented/feature/2026-07-14-cross-family-fs-sandbox.md) for cross-family policy use.
+
+The subsystem reference — modes and enforcement, per-call policy, wrapped-argv dialects, fail-closed errors — is [docs/subsystems/sandbox.md](../../docs/subsystems/sandbox.md); the boundary and the cross-family phase live in the [sandbox](../../.agents/notes/implemented/feature/2026-07-06-sandbox.md) and [cross-family fs sandbox](../../.agents/notes/implemented/feature/2026-07-14-cross-family-fs-sandbox.md) Agent Notes.

packages/sandbox/README.zh.md

@@ -11,3 +11,5 @@
 | [`sandbox-policy/`](sandbox-policy/README.md) | 解析持久的逐会话沙箱策略 | `ctx.sandboxPolicy` |
 
 [沙箱决策](../../.agents/notes/implemented/feature/2026-07-06-sandbox.md)记录了能力边界，[文件系统集成决策](../../.agents/notes/implemented/feature/2026-07-14-cross-family-fs-sandbox.md)记录了跨家族策略的使用方式。
+
+子系统参考——模式与强制执行、按调用策略、包装 argv 方言、故障关闭错误——见 [docs/subsystems/sandbox.md](../../docs/subsystems/sandbox.md)；边界与跨家族阶段见[沙箱](../../.agents/notes/implemented/feature/2026-07-06-sandbox.md)与[跨家族 fs 沙箱](../../.agents/notes/implemented/feature/2026-07-14-cross-family-fs-sandbox.md) Agent Note。