feat(telemetry): adopt from the construction boundary — constructor seeds never re-export

A cursor-less adoption (process restart + resume, fork, seam-module
reload) replayed the session's full log from seq 0, re-exporting
history that already left the process — a resume re-billed its entire
stored log on every restart, and a fork re-shipped the parent's prefix
under the child's id, doubling query-time counts on OTLP backends with
no native ingest dedupe.

dsh-session now exposes the fact the constructor already validated but
discarded: Session.firstLiveSeq, the constructor-seed length — the
first seq appended in this process. header.seedLength cannot serve
here: it is the durable fork-lineage boundary, and a resumed session's
constructor seed is its full stored log while the header keeps the
original fork value (llm-replay and session-query-sqlite depend on
that meaning). Constructor seeds also never publish on the
session/event firehose, so adoption replaying them was inconsistent
with the system's own publication semantics.

Adoption's cursor-less fallback starts at firstLiveSeq; seed events
still feed the chunk projection, so mid-step continuations re-drop
after a resume. Fork streams are no longer self-contained: records now
carry session.seed_length (with the existing session.parent_id) so
receivers stitch the child's stream onto the parent's. Accepted cost,
consistent with at-most-once delivery and recorded in the revival
Agent Note: a resume no longer backfills records a previous process
failed to deliver — a deployment with that requirement needs the
deferred outbox, not replay.

Pinned red-first: seeded adoption exports nothing (assertion reversed
from the prior seed-readback test, obsolete behavior changed with its
test), resume-shaped seed rebuilds the projection without exporting,
and fork records carry the stitch attributes.

packages/telemetry/session-telemetry-otel/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
-README.md: 28fffc5f43f960de1a44700aa70050d792b81d4f
-README.zh.md: 821969fea09487d9d4450e981a0d791a66dad3a1
+README.md: 8dd2c4f6535d6d3ea772f7669185f62c4694ca43
+README.zh.md: 42bc9b7ddbbf6d9cb104de35d9489e6e583e1df7

packages/telemetry/session-telemetry-otel/README.md

@@ -25,7 +25,7 @@ Records carry the complete `event.data` as the seam's `telemetry/redact` waterfa
 
 ## Field mapping
 
-Seam record → SDK log record: `time` → `timestamp`/`observedTimestamp`; `severity` → `severityNumber`/`severityText` (INFO 9 / WARN 13 / ERROR 17); `body` → the structured log body; `attributes` verbatim. Receivers dedupe on `(session.id, event.seq)`, alert on severity, and detect crashes by `shutdown`-record absence (a session with activity, no `shutdown` ops record, gone stale ended uncleanly). The marker means telemetry stopped observing the session cleanly — emitted at the session's own disposal, or at application teardown for sessions still running then; a marker followed by more of that session's events is a telemetry reload, not a session restart.
+Seam record → SDK log record: `time` → `timestamp`/`observedTimestamp`; `severity` → `severityNumber`/`severityText` (INFO 9 / WARN 13 / ERROR 17); `body` → the structured log body; `attributes` verbatim. Receivers dedupe on `(session.id, event.seq)`, alert on severity, and detect crashes by `shutdown`-record absence (a session with activity, no `shutdown` ops record, gone stale ended uncleanly). The marker means telemetry stopped observing the session cleanly — emitted at the session's own disposal, or at application teardown for sessions still running then; a marker followed by more of that session's events is a telemetry reload, not a session restart. Streams are not self-contained across lineage: a resumed session continues its own id's stream from where the previous process left off, and a forked session's stream starts at its inherited boundary — its prefix lives in the parent's stream, stitched via `session.parent_id` + `session.seed_length`.
 
 ## Model Experience
 

packages/telemetry/session-telemetry-otel/README.zh.md

@@ -25,7 +25,7 @@
 
 ## 字段映射
 
-seam 记录 → SDK 日志记录：`time` → `timestamp`/`observedTimestamp`；`severity` → `severityNumber`/`severityText`（INFO 9 / WARN 13 / ERROR 17）；`body` → 结构化日志 body；`attributes` 原样照搬。接收端基于 `(session.id, event.seq)` 去重、按严重级别告警，并通过 `shutdown` 记录的缺失检测崩溃（一个曾有活动、没有 `shutdown` 运维记录、且已然陈旧的会话，就是未干净结束的会话）。该标记的含义是遥测干净地停止了对该会话的观察：它在会话自身 dispose（资源释放）时发出，对于届时仍在运行的会话，则在应用拆卸时发出；标记之后又出现该会话的更多事件，说明发生的是遥测重载，而不是会话重启。
+seam 记录 → SDK 日志记录：`time` → `timestamp`/`observedTimestamp`；`severity` → `severityNumber`/`severityText`（INFO 9 / WARN 13 / ERROR 17）；`body` → 结构化日志 body；`attributes` 原样照搬。接收端基于 `(session.id, event.seq)` 去重、按严重级别告警，并通过 `shutdown` 记录的缺失检测崩溃（一个曾有活动、没有 `shutdown` 运维记录、且已然陈旧的会话，就是未干净结束的会话）。该标记的含义是遥测干净地停止了对该会话的观察：它在会话自身 dispose（资源释放）时发出，对于届时仍在运行的会话，则在应用拆卸时发出；标记之后又出现该会话的更多事件，说明发生的是遥测重载，而不是会话重启。跨谱系（lineage）的流并不自足：恢复的会话在其自身 id 的流上从上一个进程停止之处继续；fork 出的会话，其流从继承边界开始，前缀位于父会话的流中，由接收端基于 `session.parent_id` + `session.seed_length` 拼接。
 
 ## 模型体验