Fix Open with AI button to include current URL in prompt

[brittonhayes]

Summary

• The "Open in Claude/ChatGPT/Perplexity" buttons now embed the current page URL directly in the AI prompt, so the agent can fetch the page content itself
• For doc pages with .md files, the prompt includes both the .md URL and the page URL
• For API pages, the prompt includes the page URL and a reference to llms.txt for site-wide context
• Markdown is always copied to clipboard as a convenience fallback

Test plan

• Click "Open in Claude" on a docs page (e.g. /docs/introduction) — verify the prompt contains both the .md URL and the page URL
• Click "Open in Claude" on an API page (e.g. /docs/api/...) — verify the prompt contains the page URL and llms.txt reference
• Verify "Open in ChatGPT" and "Open in Perplexity" also include the URL
• Verify "Copy page" still works as before

🤖 Generated with Claude Code