feat(workbench): paginate session rail history

internal/cloud/server-workbench-http.ts

@@ -208,23 +208,40 @@ async function authenticateWorkbenchRead(request, response, options) {
 async function handleWorkbenchSessionList(response, url, options, actor) {
   if (url.searchParams.has("projectId") || url.searchParams.has("workspaceId")) return sendJson(response, 400, workbenchError("workbench_authority_removed", "Workbench session list is keyed by sessionId only."));
   const limit = boundedLimit(url.searchParams.get("limit"));
+  const offset = cursorOffset(url.searchParams.get("cursor") ?? url.searchParams.get("after"));
   const includeSessionId = safeSessionId(url.searchParams.get("includeSessionId"));
   const includeRouteId = includeSessionId ?? safeConversationId(url.searchParams.get("includeSessionId"));
   const readModel = createWorkbenchReadModel(options, actor);
-  const sessions = await readModel.listSessions({ limit, includeRouteId });
-  const summaries = sessions.map((session) => sessionSummary(session, options)).filter(Boolean);
+  const naturalPage = await readModel.listSessions({ limit: limit + 1, offset });
+  const pageSessions = naturalPage.slice(0, limit);
+  let responseSessions = pageSessions;
+  if (includeRouteId && !pageSessions.some((session) => sessionMatchesRouteId(session, includeRouteId))) {
+    const included = await readModel.getSessionByRouteId(includeRouteId);
+    if (included) responseSessions = [included, ...pageSessions];
+  }
+  const summaries = responseSessions.map((session) => sessionSummary(session, options)).filter(Boolean);
+  const hasMore = naturalPage.length > limit;
   sendJson(response, 200, {
     ok: true,
     status: "succeeded",
     contractVersion: "workbench-sessions-v1",
     sessions: summaries,
     count: summaries.length,
-    nextCursor: null,
+    cursor: offset > 0 ? cursorFromOffset(offset) : null,
+    hasMore,
+    nextCursor: hasMore ? cursorFromOffset(offset + limit) : null,
     valuesRedacted: true,
     secretMaterialStored: false
   });
 }
 
+function sessionMatchesRouteId(session, routeId) {
+  const sessionId = safeSessionId(routeId);
+  if (sessionId && session?.id === sessionId) return true;
+  const conversationId = safeConversationId(routeId);
+  return Boolean(conversationId && session?.conversationId === conversationId);
+}
+
 async function handleWorkbenchSessionDetail(response, options, actor, sessionId) {
   const readModel = createWorkbenchReadModel(options, actor);
   const session = await readModel.getSessionByRouteId(sessionId);