fix(tools): fetch documentation from base/docs with candidate path resolution

[Lesnak1]

Summary

The getGuide tool in tools.ts previously attempted to fetch documentation markdown from the deprecated base/web repository (https://raw.githubusercontent.com/base/web/refs/heads/master/apps/base-docs/docs/pages...), which returns 404 Not Found for all guide requests.

This PR updates the raw documentation source to target the official active base/docs repository with robust candidate extension resolution (.mdx, .md, and /index.*).

Changes

• tools.ts:
  • Target https://raw.githubusercontent.com/base/docs/master/docs/.
  • Normalize incoming guideLink (strip base URL, leading/trailing slashes, and explicit extensions).
  • Iterate through candidate file paths (.mdx, .md, /index.mdx, /index.md) to resolve documentation files reliably.
• utils.ts:
  • Update example guide link in findGuideParamsPrompt to point to current Base Account documentation (/base-account/guides/sign-and-verify-typed-data).
• sidebar.ts:
  • Gracefully handle sidebar content initialization without failing on the deprecated base/web URL.

Verification

• Tested fetching full URLs (e.g. https://docs.base.org/agents/guides/batch-calls).
• Tested relative paths (e.g. /get-started/get-funded).
• Tested explicit .mdx paths and verified invalid paths return a clean error response without throwing.
• Confirmed TypeScript builds cleanly (npx tsc).