feat(web-search): implement two-phase smart search pipeline

Add metadata-first search approach followed by targeted scraping of top URLs. Includes:
- New `smartSearchRag` method in web search service
- Metadata-only search endpoint in Tauri backend
- Bulk URL scraping capability
- Payload content override in chat messages

hooks/use-chat.ts

@@ -202,6 +202,9 @@ export function useChat() {
     systemPrompt?: string,
     options?: {
       onBeforeModelRequest?: (pendingMessages: Message[]) => Promise<void>;
+      // Quando presente, substitui SOMENTE o conteúdo da última mensagem do usuário
+      // no payload enviado ao LLM, mantendo a UI com o conteúdo original.
+      payloadContentOverride?: string;
     }
   ) => {
     setIsLoading(true);
@@ -257,12 +260,22 @@ export function useChat() {
     selectedMessages.push(lastUserMessage);
     totalTokens += estimateTokens(lastUserMessage.content);
 
-    const apiMessages = (systemPrompt 
+    // Constrói mensagens para payload, aplicando override apenas à última mensagem do usuário
+    const baseMessages = systemPrompt 
       ? [{ role: 'system', content: systemPrompt }, ...selectedMessages]
-      : selectedMessages).map(m => ({
+      : selectedMessages;
+
+    const apiMessages = baseMessages.map((m, idx) => {
+      // Detecta última mensagem do usuário
+      const isLastUser = m.role === 'user' && idx === baseMessages.length - 1;
+      const payloadContent = isLastUser && options?.payloadContentOverride
+        ? options.payloadContentOverride
+        : m.content;
+      return {
         role: m.role,
-        content: m.content // Send only content, not metadata (unless we want to inject it back)
-      }));
+        content: payloadContent,
+      };
+    });
 
     // [DEBUG INJECTION START]
     const systemMsg = apiMessages.find(m => m.role === 'system');

hooks/use-web-search.ts

@@ -119,6 +119,62 @@ export function useWebSearch() {
     }
   }, []);
 
+  /**
+   * Pipeline em duas etapas: metadados → scraping das top URLs
+   */
+  const smartSearchRag = useCallback(async (query: string, limit: number = 3): Promise<ScrapedContent[]> => {
+    if (!query || !query.trim()) {
+      return [];
+    }
+
+    setState(prev => ({
+      ...prev,
+      status: 'searching',
+      currentQuery: query,
+      error: null,
+      scrapedSources: [],
+    }));
+
+    try {
+      const settings = useSettingsStore.getState();
+      const searchConfig: SearchConfig = {
+        maxConcurrentTabs: settings.webSearch.maxConcurrentTabs,
+        totalSourcesLimit: settings.webSearch.totalSourcesLimit,
+        categories: settings.webSearch.categories,
+        userCustomSites: settings.webSearch.userCustomSites,
+        excludedDomains: settings.webSearch.excludedDomains,
+      };
+
+      // Etapa 1: metadados
+      setState(prev => ({ ...prev, status: 'searching' }));
+      const { metadata, contents } = await webSearchService.smartSearchRag(query, limit, searchConfig);
+
+      // Etapa 2: scraping
+      setState(prev => ({ ...prev, status: 'scraping' }));
+
+      // [DEBUG] metadados coletados
+      console.log('🔎 Metadados coletados:', metadata);
+
+      setState(prev => ({
+        ...prev,
+        status: 'completed',
+        scrapedSources: contents,
+        error: null,
+      }));
+
+      return contents;
+    } catch (error) {
+      const errorMessage = error instanceof Error ? error.message : 'Erro desconhecido no smartSearchRag';
+      setState(prev => ({
+        ...prev,
+        status: 'error',
+        error: errorMessage,
+        scrapedSources: [],
+      }));
+      throw error;
+    }
+  }, []);
+
   /**
    * Extrai conteúdo de uma URL
    */
@@ -169,6 +225,7 @@ export function useWebSearch() {
     ...state,
     setEnabled,
     search,
+    smartSearchRag,
     extractUrl,
     reset,
     clearCache,