Merge master after human transcript landing

packages/core/session/src/index.ts

@@ -27,7 +27,7 @@ export { interruptedTurnClosers, lastActivityTime, TOOL_NOT_STARTED, TOOL_OUTCOM
 export { decodeStorageRecord, packChunkRuns } from './chunk-rows.ts'
 export type { ChunkRow, StorageRecord } from './chunk-rows.ts'
 export type { SessionSurface, SurfaceFoldReplacement, SurfaceFoldResult } from './surface.ts'
-export { foldSurface, isSurfaceEvent, isSurfaceEligibleType } from './surface.ts'
+export { foldSurface, isAppendSurfaceEvent, isReplacementSurfaceEvent, isSurfaceEvent, isSurfaceEligibleType } from './surface.ts'
 export { canonicalHeader, foldRequestHeader, headerEquals } from './request-header.ts'
 
 /**
@@ -480,7 +480,8 @@ export class Session {
    *   the ordered surface; `sourceEventSeqs` records provenance (the seq
    *   numbers of events this one derives from). REQUIRED for
    *   {@link SurfaceEventType} events (every message-producing event must
-   *   declare how it joins the surface, the sole source of derived history) and
+   *   declare how it joins the surface, the sole source of derived model
+   *   history) and
    *   rejected by the compiler for non-surface types like `turn/start` or
    *   `assistant/chunk`.
    * @returns the logged event — its assigned `seq`/`time` plus the SNAPSHOT of