feat(session): add cross-session references

packages/session-query/session-query/src/index.ts

@@ -15,6 +15,7 @@ import type {
   SessionEventWindow,
   SessionLineageTrace,
   SessionRecord,
+  SessionSurfaceSnapshot,
 } from './types.ts'
 import {
   SESSION_QUERY_READ_WINDOW_MAX,
@@ -74,6 +75,21 @@ export class SessionQueryService extends Service {
     return tracing.eventRecords(sessionId, loaded.events)
   }
 
+  /**
+   * Read one session's complete current model surface from one corpus observation.
+   * @param sessionId - live-preferred session id to read.
+   * @returns cloned header, current surface, and raw-log capture boundary.
+   * @throws when source resolution fails or the session surface is invalid.
+   */
+  async readSurface(sessionId: SessionId): Promise<SessionSurfaceSnapshot> {
+    const loaded = await this._corpus.load(sessionId)
+    return {
+      session: structuredClone(loaded.header),
+      capturedThroughSeq: loaded.events.at(-1)?.seq ?? null,
+      events: tracing.currentSurfaceEvents(sessionId, loaded.events),
+    }
+  }
+
   /**
    * Trace known ancestry and descendants from one corpus observation.
    * @param sessionId - logical session id to trace.