💻 feat: Deeper MCP UI integration in the Chat UI (#9669)

* 💻 feat: deeper MCP UI integration in the chat UI using plugins

---------

Co-authored-by: Samuel Path <samuel.path@shopify.com>
Co-authored-by: Pierre-Luc Godin <pierreluc.godin@shopify.com>

* 💻 refactor: Migrate MCP UI resources from index-based to ID-based referencing

- Replace index-based resource markers with stable resource IDs
- Update plugin to parse \ui{resourceId} format instead of \ui0
- Refactor components to use useMessagesOperations instead of useSubmitMessage
- Add ShareMessagesProvider for UI resources in share view
- Add useConversationUIResources hook for cross-turn resource lookups
- Update parsers to generate resource IDs from content hashes
- Update all tests to use resource IDs instead of indices
- Add sandbox permissions for iframe popups
- Remove deprecated MCP tool context instructions

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Co-authored-by: Pierre-Luc Godin <pierreluc.godin@shopify.com>

client/src/components/Share/ShareMessagesProvider.tsx

@@ -0,0 +1,44 @@
+import React, { useMemo } from 'react';
+import type { TMessage } from 'librechat-data-provider';
+import { MessagesViewContext } from '~/Providers/MessagesViewContext';
+import type { MessagesViewContextValue } from '~/Providers/MessagesViewContext';
+
+interface ShareMessagesProviderProps {
+  messages: TMessage[];
+  children: React.ReactNode;
+}
+
+/**
+ * Minimal MessagesViewContext provider for share view.
+ * Provides conversation data needed by message components.
+ * Uses the same MessagesViewContext as the main app for compatibility with existing hooks.
+ *
+ * Note: conversationId is set to undefined because share view is read-only and doesn't
+ * need to check Recoil state for in-flight messages during streaming.
+ */
+export function ShareMessagesProvider({ messages, children }: ShareMessagesProviderProps) {
+  const contextValue = useMemo<MessagesViewContextValue>(
+    () => ({
+      conversation: { conversationId: 'shared-conversation' },
+      conversationId: undefined,
+      // These are required by the context but not used in share view
+      ask: () => Promise.resolve(),
+      regenerate: () => {},
+      handleContinue: () => {},
+      latestMessage: messages[messages.length - 1] ?? null,
+      isSubmitting: false,
+      isSubmittingFamily: false,
+      abortScroll: false,
+      setAbortScroll: () => {},
+      index: 0,
+      setLatestMessage: () => {},
+      getMessages: () => messages,
+      setMessages: () => {},
+    }),
+    [messages],
+  );
+
+  return (
+    <MessagesViewContext.Provider value={contextValue}>{children}</MessagesViewContext.Provider>
+  );
+}

client/src/components/Share/ShareView.tsx

@@ -21,6 +21,7 @@ import { ShareArtifactsContainer } from './ShareArtifacts';
 import { useLocalize, useDocumentTitle } from '~/hooks';
 import { useGetStartupConfig } from '~/data-provider';
 import { ShareContext } from '~/Providers';
+import { ShareMessagesProvider } from './ShareMessagesProvider';
 import MessagesView from './MessagesView';
 import Footer from '../Chat/Footer';
 import { cn } from '~/utils';
@@ -108,7 +109,9 @@ function SharedView() {
           onLangChange={handleLangChange}
           settingsLabel={localize('com_nav_settings')}
         />
-        <MessagesView messagesTree={messagesTree} conversationId={data.conversationId} />
+        <ShareMessagesProvider messages={data.messages}>
+          <MessagesView messagesTree={messagesTree} conversationId="shared-conversation" />
+        </ShareMessagesProvider>
       </>
     );
   } else {