docs: update docs and readme

docs/en/tools/web-fetch.mdx

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+---
+title: web_fetch - Web Fetch
+description: Fetch web pages and document content
+---
+
+Fetch the content of an HTTP/HTTPS URL. Web pages are extracted as readable text; document files (PDF, Word, Excel, etc.) are downloaded and parsed automatically.
+
+## Parameters
+
+| Parameter | Type | Required | Description |
+| --- | --- | --- | --- |
+| `url` | string | Yes | HTTP/HTTPS URL (web page or document) |
+
+## Supported file types
+
+| Type | Formats |
+| --- | --- |
+| PDF | `.pdf` |
+| Word | `.docx` |
+| Text | `.txt`, `.md`, `.csv`, `.log` |
+| Spreadsheet | `.xls`, `.xlsx` |
+| Presentation | `.ppt`, `.pptx` |
+
+## Use cases
+
+- Extract readable text from a web page
+- Download and parse remote documents
+- Inspect API response bodies
+
+<Note>
+  `web_fetch` only retrieves static HTML. For pages that require JavaScript rendering (such as SPAs), use the `browser` tool instead.
+</Note>