fix: surface list-fetch failures in paginated mode (#1998)

#1954 wired the list-load error off the aggregate managed stores only.
With `paginatedLists` on, those stores deliberately skip their all-page
walk, so their error is permanently null — while the paged stores that
actually drive the sidebar had no error state at all and `loadPage` had
a try/finally with no catch. A failing list showed an empty panel with
no alert and no Retry, and the connect-time `void loadPage(undefined)`
left an unhandled rejection.

- Give PagedTools/Prompts/ResourcesState observable error state: an
  `errorChange` event plus `getError()`, set in a new catch in
  `loadPage`, cleared on the next success and on disconnect. The
  rejection is still re-thrown, matching ManagedListState — callers'
  auth-recovery wrappers key off it to detect a 401.
- Catch the connect-time load's rejection (`.catch(() => {})`) now that
  the failure is recorded as state rather than lost.
- Select the error by mode in `usePaginatedList`, the same way `items`
  already is, and read it in App.tsx from the pagination model.
- Rename `useManagedListError` to `useListError`: both store families
  expose an identical `errorChange`, so the hook declares that one-event
  contract itself instead of importing ManagedListEventMap.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0177mPHAdECD18nLLCTwR5rh
Signed-off-by: cliffhall <cliff@futurescale.com>

core/react/useManagedResourceTemplates.ts

@@ -6,7 +6,7 @@ import type {
 } from "../mcp/state/managedResourceTemplatesState.js";
 import type { ResourceTemplateType as ResourceTemplate } from "@modelcontextprotocol/client";
 import type { TypedEventGeneric } from "../mcp/typedEventTarget.js";
-import { useManagedListError } from "./useManagedListError.js";
+import { useListError } from "./useListError.js";
 
 export interface UseManagedResourceTemplatesResult {
   /**
@@ -57,7 +57,7 @@ export function useManagedResourceTemplates(
     };
   }, [managedResourceTemplatesState]);
 
-  const error = useManagedListError(managedResourceTemplatesState);
+  const error = useListError(managedResourceTemplatesState);
 
   const refresh = useCallback(async (): Promise<ResourceTemplate[]> => {
     if (!managedResourceTemplatesState || !client) return [];