add official PyPI package-docs lookup

[ayhammouda]

Summary

Add package-docs lookup for official PyPI packages / package documentation.

Motivation

Today the server is intentionally stdlib-only, which keeps the trust/compliance story very clean. But in practice, many teams will immediately ask for package-level docs once they adopt the Python stdlib flow.

The request here is to expand beyond stdlib with a still-controlled scope:

• package discovery via official PyPI metadata
• package documentation lookup constrained to official/package-declared sources

Why this matters

For real development workflows, stdlib-only coverage is useful but incomplete. A lot of day-to-day engineering work happens in package ecosystems, and users will naturally want a compliant path there too.

Expected behavior

A future package-docs mode could:

• resolve a package via official PyPI metadata
• identify the package's declared documentation/homepage/source URLs
• retrieve documentation only from official package-owned sources, not arbitrary community mirrors
• keep the same explicit trust/compliance posture as the stdlib mode

Non-goal / caution

The value of this project comes from its clean trust boundary, so this should not become a generic web search tool.

If implemented, the feature should keep strong rules around:

• official PyPI metadata as the discovery source
• package-owned / canonical docs only
• explicit source visibility in results
• no silent fallback to community/unofficial sources

Open design question

This may be better as:

1. a separate MCP server/tool surface for package docs, or
2. an explicitly scoped extension of the current server

Either way, the compliance model should stay obvious and auditable.