feat(collab): separate agent edits from human edits in page history

Page-history snapshots are debounced/coalesced (one per 1–5 min window,
jobId=page.id). A human edit followed by an agent edit in the same window
collapsed into a single snapshot, losing both the pre-agent human state and
a deterministic record of the agent's result.

Two provenance-aware boundaries now bracket an agent intervention:
- Before: on a user->agent transition, onStoreDocument synchronously pins the
  current (pre-agent) human content as its own history version tagged 'user',
  inside the page-write transaction, before the agent overwrites it.
- After: agent stores enqueue an immediate (delay 0), source-keyed history job
  (jobId=`${pageId}:agent`) so the agent's result snapshots deterministically
  as 'agent' and a later human edit (jobId=page.id) cannot coalesce/retag it.

Also add an `id desc` tie-break to findPageLastHistory so "last history" stays
deterministic when two snapshots share a created_at, consistent with
findPageHistoryByPageId.

Known trade-offs (Variant 1): the delay-0 worker re-reads the row, leaving a
millisecond mis-tag window; multiple agent edits in one turn may yield multiple
versions. The reverse agent->human boundary is intentionally out of scope.

apps/server/src/collaboration/extensions/persistence.extension.ts

@@ -8,8 +8,14 @@ import {
 import * as Y from 'yjs';
 import { Injectable, Logger } from '@nestjs/common';
 import { TiptapTransformer } from '@hocuspocus/transformer';
-import { getPageId, jsonToText, tiptapExtensions } from '../collaboration.util';
+import {
+  getPageId,
+  isEmptyParagraphDoc,
+  jsonToText,
+  tiptapExtensions,
+} from '../collaboration.util';
 import { PageRepo } from '@docmost/db/repos/page/page.repo';
+import { PageHistoryRepo } from '@docmost/db/repos/page/page-history.repo';
 import { InjectKysely } from 'nestjs-kysely';
 import { KyselyDB } from '@docmost/db/types/kysely.types';
 import { executeTx } from '@docmost/db/utils';
@@ -46,6 +52,7 @@ export class PersistenceExtension implements Extension {
 
   constructor(
     private readonly pageRepo: PageRepo,
+    private readonly pageHistoryRepo: PageHistoryRepo,
     @InjectKysely() private readonly db: KyselyDB,
     @InjectQueue(QueueName.AI_QUEUE) private aiQueue: Queue,
     @InjectQueue(QueueName.HISTORY_QUEUE) private historyQueue: Queue,
@@ -157,6 +164,32 @@ export class PersistenceExtension implements Extension {
           //this.logger.debug('Contributors error:' + err?.['message']);
         }
 
+        // Approach A — boundary snapshot before the agent's first edit.
+        // When this store is the agent's and the page's currently persisted
+        // state was authored by a human, pin that human state as its own
+        // history version BEFORE the agent overwrites it. `page` still holds the
+        // OLD content/provenance here, so saveHistory(page) captures the
+        // pre-agent state tagged 'user'. The agent's new content is snapshotted
+        // later by the debounced PAGE_HISTORY job ('agent'). Skip if the prior
+        // state is already agent-authored (boundary already pinned on the
+        // user->agent transition), if the page is effectively empty, or if the
+        // latest existing snapshot already equals this human state (avoid
+        // duplicates).
+        if (lastUpdatedSource === 'agent' && page.lastUpdatedSource !== 'agent') {
+          const lastHistory = await this.pageHistoryRepo.findPageLastHistory(
+            pageId,
+            { includeContent: true, trx },
+          );
+          const humanBaselineMissing =
+            !lastHistory || !isDeepStrictEqual(lastHistory.content, page.content);
+          if (!isEmptyParagraphDoc(page.content as any) && humanBaselineMissing) {
+            await this.pageHistoryRepo.saveHistory(page, {
+              contributorIds: page.contributorIds ?? undefined,
+              trx,
+            });
+          }
+        }
+
         await this.pageRepo.updatePage(
           {
             content: tiptapJson,
@@ -229,7 +262,7 @@ export class PersistenceExtension implements Extension {
         workspaceId: page.workspaceId,
       });
 
-      await this.enqueuePageHistory(page);
+      await this.enqueuePageHistory(page, lastUpdatedSource);
     }
   }
 
@@ -273,17 +306,30 @@ export class PersistenceExtension implements Extension {
     return touched;
   }
 
-  private async enqueuePageHistory(page: Page): Promise<void> {
+  private async enqueuePageHistory(
+    page: Page,
+    lastUpdatedSource: string,
+  ): Promise<void> {
+    // Agent edits get an immediate, source-keyed history job: they snapshot
+    // deterministically as 'agent' and a later human edit (jobId = page.id)
+    // cannot coalesce/retag them. Human edits keep the age-based debounce so
+    // rapid human edits still coalesce into one snapshot.
+    // NOTE: the agent delay MUST stay 0 — the worker re-reads the page row at
+    // run time, so any delay would risk reading content a later human edit has
+    // already overwritten (mis-tagged snapshot). 0 minimizes that window.
+    const isAgent = lastUpdatedSource === 'agent';
     const pageAge = Date.now() - new Date(page.createdAt).getTime();
-    const delay =
-      pageAge < HISTORY_FAST_THRESHOLD
+    const delay = isAgent
+      ? 0
+      : pageAge < HISTORY_FAST_THRESHOLD
         ? HISTORY_FAST_INTERVAL
         : HISTORY_INTERVAL;
+    const jobId = isAgent ? `${page.id}:agent` : page.id;
 
     await this.historyQueue.add(
       QueueJob.PAGE_HISTORY,
       { pageId: page.id } as IPageHistoryJob,
-      { jobId: page.id, delay },
+      { jobId, delay },
     );
   }