feat(#370): page-history intentionality tiers — kind column + intentional/idle/boundary triggers (PR-1 core)

PR-1 'core' of #370: introduces page_history.kind ('manual'|'agent'|'idle'|
'boundary'; legacy null = autosave) and rebuilds the snapshot triggers around a
three-tier intentionality model. Draft durability (pages/ydoc hocuspocus
autosave) is unchanged; only the frequency and labelling of history points change.

- Migration 20260705T120000: page_history.kind nullable varchar(20), no default.
- Manual Save: one stateless 'save-version' path for human AND agent; kind is
  derived SERVER-SIDE from the signed context.actor (never the payload), readOnly
  connections rejected, the fresh ydoc runs through the existing store path (no
  REST race), then broadcasts version.saved.
- Idle-flush: trailing debounce (one BullMQ job per page, remove-then-readd) with
  IDLE_INTERVAL_USER=60m / AGENT=15m AND a max-wait ceiling
  (IDLE_MAX_WAIT_USER=10m / AGENT=5m) so a continuous editing session can't starve
  the autosnapshot (review round-1 WARNING).
- Boundary: generalized from the user→agent special-case to ANY lastUpdatedSource
  transition (user↔agent↔git), same isDeepStrictEqual gate — covers git-sync free.
- Removed the agent delay=0 fast path and the old HISTORY_FAST_* constants; the
  agent joins the common idle pipeline.
- Promote-not-dup: a manual save on unchanged content promotes the latest
  autosave's kind in place (or no-ops if already manual) instead of duplicating a
  heavy content row.
- Client: mod+S hotkey + menu button (hidden when readOnly), history-panel kind
  badges, dimmed autosaves, a 'versions only' filter (indices map to the full
  list so diff/restore still target the true previous snapshot), live refresh on
  version.saved.

Internal review: APPROVE-with-suggestions; the round-1 WARNING (idle starvation)
is fixed here via the max-wait ceiling, and the generalized-boundary + ceiling
behaviours are pinned with new tests (115 collab/repo specs green, server tsc 0).

Deferred to later PRs: shares.published_mode (PR-2), the save_page_version MCP
tool + role prompts (PR-3), actor='git' wiring into #359 (PR-4).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/src/features/editor/page-editor.tsx

@@ -31,11 +31,18 @@ import { useAtom, useAtomValue, useSetAtom } from "jotai";
 import useCollaborationUrl from "@/features/editor/hooks/use-collaboration-url";
 import { currentUserAtom } from "@/features/user/atoms/current-user-atom";
 import {
+  collabProviderAtom,
   currentPageEditModeAtom,
   dictationAvailabilityAtom,
   pageEditorAtom,
   yjsConnectionStatusAtom,
 } from "@/features/editor/atoms/editor-atoms";
+import { notifications } from "@mantine/notifications";
+import {
+  VERSION_SAVED_MESSAGE_TYPE,
+  type VersionSavedMessage,
+  saveVersionPending,
+} from "@/features/page-history/version-messages";
 import { asideStateAtom } from "@/components/layouts/global/hooks/atoms/sidebar-atom";
 import {
   activeCommentIdAtom,
@@ -124,6 +131,7 @@ export default function PageEditor({
 
   const [currentUser] = useAtom(currentUserAtom);
   const [, setEditor] = useAtom(pageEditorAtom);
+  const setCollabProvider = useSetAtom(collabProviderAtom);
   const [, setAsideState] = useAtom(asideStateAtom);
   const [, setActiveCommentId] = useAtom(activeCommentIdAtom);
   const [showCommentPopup, setShowCommentPopup] = useAtom(showCommentPopupAtom);
@@ -181,6 +189,24 @@ export default function PageEditor({
       const onStatelessHandler = ({ payload }: onStatelessParameters) => {
         try {
           const message = JSON.parse(payload);
+          // #370 — a version was saved somewhere; live-refresh the history panel
+          // on every client. Only the client that pressed Save (tracked by the
+          // module-level flag) shows the confirmation toast.
+          if (message?.type === VERSION_SAVED_MESSAGE_TYPE) {
+            const versionMsg = message as VersionSavedMessage;
+            queryClient.invalidateQueries({
+              queryKey: ["page-history-list"],
+            });
+            if (saveVersionPending.current) {
+              saveVersionPending.current = false;
+              notifications.show({
+                message: versionMsg.alreadySaved
+                  ? t("Already saved as the latest version")
+                  : t("Version saved"),
+              });
+            }
+            return;
+          }
           if (message?.type !== "page.updated" || !message.updatedAt) return;
           const pageData = queryClient.getQueryData<IPage>(["pages", slugId]);
           if (pageData) {
@@ -238,12 +264,16 @@ export default function PageEditor({
 
       local.on("synced", onLocalSyncedHandler);
       providersRef.current = { socket, local, remote };
+      // #370 — publish the provider so the header menu can emit save-version.
+      setCollabProvider(remote);
       setProvidersReady(true);
     } else {
+      setCollabProvider(providersRef.current.remote);
       setProvidersReady(true);
     }
     // Only destroy on final unmount
     return () => {
+      setCollabProvider(null);
       providersRef.current?.socket.destroy();
       providersRef.current?.remote.destroy();
       providersRef.current?.local.destroy();