🧩 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.

packages/api/src/tools/toolkits/index.ts

@@ -1,3 +1,4 @@
 export * from './gemini';
 export * from './imageContext';
 export * from './oai';
+export * from './web';

packages/api/src/tools/toolkits/web.ts

@@ -0,0 +1,23 @@
+import { Tools, replaceSpecialVars } from 'librechat-data-provider';
+
+/** Builds the web search tool context with citation format instructions. */
+export function buildWebSearchContext(): string {
+  return `# \`${Tools.web_search}\`:
+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();
+}