round 1: project the web transcript from append-origin events

Replace the surface-ordered fold with a log-ordered human transcript:
append-origin surface events at their own log positions plus one marker per
landed compaction checkpoint. Command folding, the tool-call index, and the
rev-keyed memo carry over unchanged.

Removes foldDegraded, the padding sentinels, baseSeq, and degradedSeqs() --
they existed only to satisfy the core fold's seq === index assertion. That
also closes the pagination hole A1 exposed: a page can carry a checkpoint
whose shadowed range fell outside the window, and nothing resolves
surfaceOp.start anymore.

.agents/notes/implemented/architecture/2026-07-19-gui-web-client-architecture.md

@@ -50,7 +50,7 @@ There is no registration model besides slots — the former view and tool rings
 
 ## The data object layer (`packages/client/runtime/src/client/sessions/`)
 
-Frames enter, snapshots exit, the fold sits between — React-free (zero React imports, grep-assertable):
+Frames enter, snapshots exit, the projection sits between — React-free (zero React imports, grep-assertable):
 
 ```
 mux/host 帧（ConnectionController 泵入，sinks 注入）
@@ -62,17 +62,17 @@ SessionManager.handleMuxEnvelope / handleHostEnvelope
 Session.handleMuxEnvelope ──► events 窗口（seq 连续升序）
         │                        │ 定稿事件            │ chunk
         │                        ▼                    ▼
-        │                   FoldAdapter        PartialAccumulator
+        │                TranscriptAdapter     PartialAccumulator
         │                  （→ nodes）          （→ partial）
         ▼
 Notifier 微任务合批 ──► ConversationSnapshot 缓存 ──uSES──► 组件
 ```
 
-- **Session** (session.ts): lazily built, resident — once created it keeps eating frames in the background, so switching away and back renders instantly. Operations: `prompt`/`cancel` (RPC passthrough; failures land in the snapshot's `promptError`), `open` (pull the tail history page, idempotent), `loadOlder` (upward paging, reentry-guarded), `resync` (reconnect = clear the window and rerun open). Subscription: `subscribe`/`getSnapshot` (always the cached reference) — `implements ObservableSnapshot<ConversationSnapshot>`, with `useSelector = bindSnapshotSelector(this)` attached at construction, so a Session is directly a uSES source. Frame dispatch is one switch: `session/event` frames dedup by seq (the only dedup key), buffer while open is in flight, otherwise append + incremental fold; open/stitch merges the live buffer by seq and backfills once if `subscribed.lastSeq` outruns the window tail.
-- **ConversationSnapshot** (conversation.ts): the immutable snapshot contract — `nodes` (folded, surface-ordered), `partial`, `runningCalls`, `pending`, `running`, `removed`, `openState`, `hasMore`, `promptError` and kin. **Reference discipline** (the premise of memo and uSES): the top-level object is fresh on every change; the nodes array is rebuilt but element references come from the cache; unchanged substructures reuse the previous snapshot's references.
+- **Session** (session.ts): lazily built, resident — once created it keeps eating frames in the background, so switching away and back renders instantly. Operations: `prompt`/`cancel` (RPC passthrough; failures land in the snapshot's `promptError`), `open` (pull the tail history page, idempotent), `loadOlder` (upward paging, reentry-guarded), `resync` (reconnect = clear the window and rerun open). Subscription: `subscribe`/`getSnapshot` (always the cached reference) — `implements ObservableSnapshot<ConversationSnapshot>`, with `useSelector = bindSnapshotSelector(this)` attached at construction, so a Session is directly a uSES source. Frame dispatch is one switch: `session/event` frames dedup by seq (the only dedup key), buffer while open is in flight, otherwise append + incremental projection; open/stitch merges the live buffer by seq and backfills once if `subscribed.lastSeq` outruns the window tail.
+- **ConversationSnapshot** (conversation.ts): the immutable snapshot contract — `nodes` (the human transcript, log-ordered), `partial`, `runningCalls`, `pending`, `running`, `removed`, `openState`, `hasMore`, `promptError` and kin. **Reference discipline** (the premise of memo and uSES): the top-level object is fresh on every change; the nodes array is rebuilt but element references come from the cache; unchanged substructures reuse the previous snapshot's references.
 - **SessionManager** (manager.ts): instance cluster + frame entry + the session list. sessionId-bearing frames go only to existing instances (a mux broadcast must not instantiate every session); approval/question `requested` frames are the exception — they never land in history, so they buffer in `pendingBuffers` and replay on instantiation.
 - **Notifier** (notifier.ts): two channels chosen by change source. `markDirty()` (default; frame-driven changes always) batches per microtask — N changes, one notification, one re-render; the flush rebuilds the snapshot cache before notifying. `notifyNow()` (only direct echoes of user gestures) rebuilds and notifies in the same tick — controlled inputs roll the DOM back and jump the caret if their echo defers to a microtask. Frame-driven code using notifyNow collapses batching back to per-frame renders; banned.
-- **FoldAdapter / PartialAccumulator**: the fold reuses the core SurfaceManager (`@deepseek-ai/dsh-session/surface`), padding sentinel events so a paged window starting at seq > 0 satisfies the core's `seq === index` assertion; a cross-window replace degrades to a tolerant linear scan and sets `foldDegraded`. Chunks stay out of the fold entirely (O(1) skip): the accumulator folds StreamChunks into `AssistantBlock[]`, a delta swapping only that block's reference, and the finalizing message discards the accumulator in the same batch (no flicker on promotion). Cost model: one chunk = one string concatenation + a dirty mark; an unsubscribed Session under a frame storm costs only the mark.
+- **TranscriptAdapter / PartialAccumulator**: the transcript is the append-origin surface projected in log order (`isAppendSurfaceEvent` from `@deepseek-ai/dsh-session/surface`) plus one marker per landed compaction checkpoint — never the model surface, which shadows replaced ranges and would erase conversation the reader already saw. Node order is seq-monotonic by construction, so there is no core `seq === index` assertion to satisfy and no degradation branch. Chunks contribute no node (O(1) skip): the accumulator folds StreamChunks into `AssistantBlock[]`, a delta swapping only that block's reference, and the finalizing message discards the accumulator in the same batch (no flicker on promotion). Cost model: one chunk = one string concatenation + a dirty mark; an unsubscribed Session under a frame storm costs only the mark.
 - **ConnectionController** (in `packages/client/connection`): opens the mux/host streams, pumps with for-await, reconnects with exponential backoff (500ms doubling to 10s, jitter, unlimited) behind a generation fence; sinks are injected one-way (the Controller does not know Session). Reconnect = rebuild: `onConnected` → list refresh + per-open-session resync. The object layer faces only `IApiClient`; the Web carriage (HTTP POST for the two client→server quadrants, SSE for the two server→client) and the client class family are the layering RFC's territory.
 
 ## The React face (`packages/client/web-react`)