Merge remote-tracking branch 'origin/master' into feat/todo-multi-in-progress

docs/core-data-structures/session.md

@@ -370,6 +370,18 @@ declare class Session {
   readonly header: SessionHeader;
   /** The session identity, derived from its durable header's single copy. */
   get id(): SessionId;
+  /**
+   * The first seq appended IN THIS PROCESS: the length of the constructor
+   * seed (0 without one). Events below it entered through construction —
+   * replay, fork, or resume — and were never published on the `session/event`
+   * firehose (constructor seeds do not emit), so consumers that replay the
+   * log as a publication substitute (telemetry adoption) start here. Distinct
+   * from `header.seedLength`, the DURABLE fork-lineage boundary: a resumed
+   * session's constructor seed is its full stored log, while its header keeps
+   * the original fork value — this field is the in-process construction fact
+   * and is deliberately not persisted.
+   */
+  readonly firstLiveSeq: number;
   constructor(id: SessionId, seed?: readonly SessionEvent[], header?: SessionHeader);
   /**
    * An immutable snapshot of the append-only event log. The snapshot is reused