feat: add arxiv and wikipedia to built-in commands table

[BruceLoveDecimal]

Description

Add two new public API adapters: arXiv and Wikipedia.

Both are PUBLIC strategy with browser: false — no login or Browser Bridge extension required.

arXiv (src/clis/arxiv/)

• search <keyword> — search papers by keyword, sorted by relevance
• paper <id> — get paper details by arXiv ID (e.g. 1706.03762)
• Parses the public Atom/XML API without any extra dependencies

Wikipedia (src/clis/wikipedia/)

• search <keyword> — search articles via MediaWiki Action API
• summary <title> — get article summary via REST API v1
• Supports --lang for multilingual queries (en, zh, ja, etc.)

Related issue:

Type of Change

• 🌐 New site adapter

Checklist

• I ran the checks relevant to this PR
• I updated tests or docs if needed
• I included output or screenshots when useful

Screenshots / Output

$ opencli arxiv search "attention is all you need" --limit 3
$ opencli arxiv paper 1706.03762
$ opencli wikipedia search "transformer"
$ opencli wikipedia summary "Transformer (machine learning model)"
$ opencli wikipedia search "人工智能" --lang zh

[BruceLoveDecimal]

好像关于小红书的UT有点问题？