refactor(session): drop the unused predicate helper and tighten the docs

`isInheritedSeq` had no production caller — only its own tests — so it was
a public core export shaped by nothing. A bracket owner reads the boundary
positionally; the helper belongs with the compaction seam, where a real
consumer decides its signature.

Also condense the `session/inherited` and `lastActivityTime` docs.

.agents/notes/implemented/architecture/2026-07-30-session-inherited-log-boundary.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 .agents/notes/implemented/architecture/2026-07-30-session-inherited-log-boundary.md
-2026-07-30-session-inherited-log-boundary.md: 027281a7555214122b4e2d1f8457d3554a751921
-2026-07-30-session-inherited-log-boundary.zh.md: 3c169e16f0b409f125ccc29226412f239a58c6aa
+2026-07-30-session-inherited-log-boundary.md: 3b9cb09d1d1a16d30fd212b439a97e3d9296bd6d
+2026-07-30-session-inherited-log-boundary.zh.md: de048bc994ca97f937f74783b9055fbeb171314a

.agents/notes/implemented/architecture/2026-07-30-session-inherited-log-boundary.md

@@ -16,9 +16,9 @@ Crash repair does not close the gap and must not: `interruptedTurnClosers` synth
 
 `Session`'s constructor appends the log-only `session/inherited` event as the seeded session's first live write, at the seq `firstLiveSeq` names. The event is the durable projection of that field: `firstLiveSeq` answers "which prefix did I inherit" for a consumer holding the object, the event answers it for one holding only stored bytes. Its payload is empty — position and `time` carry the whole meaning — and it is not a `SurfaceEventType`, so it produces no message and cannot perturb derived history.
 
-`isInheritedSeq(events, seq)` (exported from `dsh-session`) is the predicate a bracket owner calls on an unmatched opening marker. True means the marker belongs to a lifecycle that has ended and cannot still be running. Core writes the boundary and reads nothing from it; each bracket's vocabulary stays with its owning plugin.
+A bracket owner reads it positionally: an unmatched opening marker below the boundary belongs to a lifecycle that has ended and cannot still be running. Core writes the boundary and reads nothing from it; each bracket's vocabulary stays with its owning plugin, so no core predicate helper ships without a consumer to shape it.
 
-The constructor is the placement because it is the single waist every seeded session passes through. All six entry points reach it: `agents.resume()`, config-driven startup on a persisted id (`restoreOrCreateConfigured`), `sessions.fork()`, a subagent fork child, `coordinator.adopt()`'s live-prefix path, and a bare `sessions.create(id, {seed})`. A boundary written at persistence load would miss both fork paths — and a forked child inheriting a still-running parent's open `compact/start` is precisely the case the predicate must classify. A boundary written at loop start would miss `fork()` and `adopt()`, and would have to fire on `SessionStartSource: 'startup'`, which is what a fork child publishes, so that field would stop discriminating.
+The constructor is the placement because it is the single waist every seeded session passes through. All six entry points reach it: `agents.resume()`, config-driven startup on a persisted id (`restoreOrCreateConfigured`), `sessions.fork()`, a subagent fork child, `coordinator.adopt()`'s live-prefix path, and a bare `sessions.create(id, {seed})`. A boundary written at persistence load would miss both fork paths — and a forked child inheriting a still-running parent's open `compact/start` is precisely the case that must be classifiable. A boundary written at loop start would miss `fork()` and `adopt()`, and would have to fire on `SessionStartSource: 'startup'`, which is what a fork child publishes, so that field would stop discriminating.
 
 Two guards keep the marker from becoming noise. An empty seed writes nothing: a boundary with nothing below it marks nothing. A seed already ending in one is not re-marked, which makes the write idempotent. Idempotence is load-bearing rather than tidiness — `agentFor()` resumes a cold session on first touch, so merely opening one in a client is a pickup, and without the guard browsing would grow a log by one event per visit.
 
@@ -44,10 +44,10 @@ The predicate holds for a bracket *this* session inherited, not as a liveness si
 
 ## Consequences
 
-Bought: one predicate, in one place, correct for all six seeded-start paths — including the fork gap the persistence-layer version could not reach. The persistence packages keep a pure read path. `firstLiveSeq` gains a durable twin rather than a second, competing notion of the same boundary.
+Bought: one boundary, written in one place, correct for all six seeded-start paths — including the fork gap the persistence-layer version could not reach. The persistence packages keep a pure read path. `firstLiveSeq` gains a durable twin rather than a second, competing notion of the same boundary.
 
 Cost: a seeded session's log is one event longer, which moved seq expectations in tests across nine packages (session, agent-loop, persistence contract, jsonl, session-query, session-title, subagent-inprocess, telemetry, token-meter). Two of those updates are load-bearing rather than mechanical: telemetry's adoption tests now assert the boundary IS exported, because it is this lifecycle's own write, and the property suite's replay invariant is restated as "seed reproduced verbatim, plus one log-only boundary" with idempotence added as its own property.
 
 `session/inherited` joins the on-disk vocabulary. Under the pre-release stance (`SESSION_FORMAT_VERSION` pinned at `0`, no compatibility promise) older logs simply lack it, and a log without a boundary correctly reports nothing as inherited.
 
-Not built here: no plugin consumes `isInheritedSeq` yet. Wiring the compaction seam's staleness check to it is the follow-up that motivated this boundary, and it belongs with that seam's own tests.
+Not built here: no plugin reads the boundary yet. Wiring the compaction seam's staleness check to it is the follow-up that motivated this boundary; the predicate helper belongs with that seam, where a real consumer decides its shape, rather than shipping into core untested against one.

.agents/notes/implemented/architecture/2026-07-30-session-inherited-log-boundary.zh.md

@@ -16,9 +16,9 @@ Status: implemented
 
 `Session` 的构造函数把仅日志事件 `session/inherited` 作为带种子会话的第一次实时写入追加，位置正是 `firstLiveSeq` 指出的 seq。该事件是那个字段的持久投影：`firstLiveSeq` 为持有对象的消费方回答"我继承了哪一段前缀"，该事件则为只持有存储字节的消费方回答同一问题。它的 payload 为空——位置与 `time` 承载全部含义——并且不是 `SurfaceEventType`，因此不产生消息，也无法扰动派生历史。
 
-`isInheritedSeq(events, seq)`（由 `dsh-session` 导出）是括号所有方在一个未配对开启标记上调用的谓词。为真意味着该标记属于一个已结束的生命周期，不可能仍在运行。核心写入该边界但不从中读取任何内容；每个括号的词汇表仍归其所属插件。
+括号所有方按位置读取它：位于边界之下的未配对开启标记属于一个已结束的生命周期，不可能仍在运行。核心写入该边界但不从中读取任何内容；每个括号的词汇表仍归其所属插件，因此在没有消费方来塑形之前，核心不会先发布谓词辅助函数。
 
-选择构造函数，是因为它是每一个带种子会话都必经的唯一收窄处。全部六个入口都会到达它：`agents.resume()`、在已持久化 id 上的配置驱动启动（`restoreOrCreateConfigured`）、`sessions.fork()`、子代理 fork 子会话、`coordinator.adopt()` 的实时前缀路径，以及裸的 `sessions.create(id, {seed})`。在持久化加载时写入的边界会漏掉两条 fork 路径——而一个继承了仍在运行的父会话开放 `compact/start` 的 fork 子会话，恰恰是该谓词必须判定的场景。在 loop 启动时写入的边界会漏掉 `fork()` 与 `adopt()`，并且不得不在 `SessionStartSource: 'startup'` 上触发——那正是 fork 子会话发布的取值，于是该字段将不再具有区分力。
+选择构造函数，是因为它是每一个带种子会话都必经的唯一收窄处。全部六个入口都会到达它：`agents.resume()`、在已持久化 id 上的配置驱动启动（`restoreOrCreateConfigured`）、`sessions.fork()`、子代理 fork 子会话、`coordinator.adopt()` 的实时前缀路径，以及裸的 `sessions.create(id, {seed})`。在持久化加载时写入的边界会漏掉两条 fork 路径——而一个继承了仍在运行的父会话开放 `compact/start` 的 fork 子会话，恰恰是必须可判定的场景。在 loop 启动时写入的边界会漏掉 `fork()` 与 `adopt()`，并且不得不在 `SessionStartSource: 'startup'` 上触发——那正是 fork 子会话发布的取值，于是该字段将不再具有区分力。
 
 两条守卫让这个标记不至于变成噪声。空种子不写入任何内容：下方什么都没有的边界标记不了任何东西。种子本身已以该事件结尾时不会重复标记，这让写入具备幂等性。幂等性是承重的，而不是为了整洁——`agentFor()` 会在首次触碰时恢复一个冷会话，因此在客户端里仅仅打开一个会话就是一次接手；没有这条守卫，浏览会让日志每访问一次就增长一个事件。
 
@@ -44,10 +44,10 @@ Status: implemented
 
 ## Consequences
 
-买到的：一个谓词，位于一处，对全部六条带种子启动路径都正确——包括持久化层方案触及不到的 fork 缺口。持久化各包保留纯读取路径。`firstLiveSeq` 获得一个持久孪生体，而不是关于同一边界的第二套彼此竞争的概念。
+买到的：一条边界，在一处写入，对全部六条带种子启动路径都正确——包括持久化层方案触及不到的 fork 缺口。持久化各包保留纯读取路径。`firstLiveSeq` 获得一个持久孪生体，而不是关于同一边界的第二套彼此竞争的概念。
 
 代价：带种子会话的日志长了一个事件，这在九个包（session、agent-loop、持久化契约、jsonl、session-query、session-title、subagent-inprocess、telemetry、token-meter）里挪动了 seq 期望。其中两处更新是承重的而非机械的：telemetry 的收养测试现在断言该边界*会*被导出，因为它是本生命周期的自有写入；而属性测试套件的重放不变式被重述为"种子逐字节复现，外加一个仅日志边界"，并把幂等性补成一条独立属性。
 
 `session/inherited` 加入了落盘词汇表。在预发布立场下（`SESSION_FORMAT_VERSION` 固定为 `0`，不作兼容承诺），更旧的日志只是没有它，而没有边界的日志会正确地报告没有任何内容被继承。
 
-此处未做：还没有任何插件消费 `isInheritedSeq`。把压缩 seam 的陈旧性检查接到它上面，是催生这条边界的后续工作，应当与那个 seam 自己的测试一起完成。
+此处未做：还没有任何插件读取该边界。把压缩 seam 的陈旧性检查接到它上面，是催生这条边界的后续工作；谓词辅助函数应当归属那个 seam——在那里由真实消费方决定它的形状——而不是未经真实消费方检验就先落进核心。