🧩 refactor: Tool Context Builders for Web Search & Image Gen (#11644)

* fix: Web Search + Image Gen Tool Context

- Added `buildWebSearchContext` function to create a structured context for web search tools, including citation format instructions.
- Updated `loadTools` and `loadToolDefinitionsWrapper` functions to utilize the new web search context, improving tool initialization and response handling.
- Introduced logic to handle image editing tools with `buildImageToolContext`, enhancing the overall tool management capabilities.
- Refactored imports in `ToolService.js` to include the new context builders for better organization and maintainability.

* fix: Trim critical output escape sequence instructions in web toolkit

- Updated the critical output escape sequence instructions in the web toolkit to include a `.trim()` method, ensuring that unnecessary whitespace is removed from the output. This change enhances the consistency and reliability of the generated output.

api/app/clients/tools/util/handleTools.js

@@ -11,6 +11,7 @@ const {
   mcpToolPattern,
   loadWebSearchAuth,
   buildImageToolContext,
+  buildWebSearchContext,
 } = require('@librechat/api');
 const { getMCPServersRegistry } = require('~/config');
 const {
@@ -19,7 +20,6 @@ const {
   Permissions,
   EToolResources,
   PermissionTypes,
-  replaceSpecialVars,
 } = require('librechat-data-provider');
 const {
   availableTools,
@@ -325,24 +325,7 @@ const loadTools = async ({
       });
       const { onSearchResults, onGetHighlights } = options?.[Tools.web_search] ?? {};
       requestedTools[tool] = async () => {
-        toolContextMap[tool] = `# \`${tool}\`:
-Current Date & Time: ${replaceSpecialVars({ text: '{{iso_datetime}}' })}
-
-**Execute immediately without preface.** After search, provide a brief summary addressing the query directly, then structure your response with clear Markdown formatting (## headers, lists, tables). Cite sources properly, tailor tone to query type, and provide comprehensive details.
-
-**CITATION FORMAT - UNICODE ESCAPE SEQUENCES ONLY:**
-Use these EXACT escape sequences (copy verbatim): \\ue202 (before each anchor), \\ue200 (group start), \\ue201 (group end), \\ue203 (highlight start), \\ue204 (highlight end)
-
-Anchor pattern: \\ue202turn{N}{type}{index} where N=turn number, type=search|news|image|ref, index=0,1,2...
-
-**Examples (copy these exactly):**
-- Single: "Statement.\\ue202turn0search0"
-- Multiple: "Statement.\\ue202turn0search0\\ue202turn0news1"
-- Group: "Statement. \\ue200\\ue202turn0search0\\ue202turn0news1\\ue201"
-- Highlight: "\\ue203Cited text.\\ue204\\ue202turn0search0"
-- Image: "See photo\\ue202turn0image0."
-
-**CRITICAL:** Output escape sequences EXACTLY as shown. Do NOT substitute with † or other symbols. Place anchors AFTER punctuation. Cite every non-obvious fact/quote. NEVER use markdown links, [1], footnotes, or HTML tags.`.trim();
+        toolContextMap[tool] = buildWebSearchContext();
         return createSearchTool({
           ...result.authResult,
           onSearchResults,