Update live preview docs for cross-window architecture

[mintlify]

Summary

Updated the live preview documentation to reflect the new cross-window architecture. Live preview now opens in a separate browser window instead of being embedded in the editor, and requires both windows to remain open in the same browser session.

Changes

• Clarified that live preview opens in a separate browser window
• Updated comparison table to show "Separate window (local only)" instead of "In the editor"
• Changed button icon reference from target to media-play
• Added note about requiring both windows to be open
• Highlighted that live preview is local-only with upgrade path for shareable previews
• Changed authentication limitation from Note to Warning for better visibility

Generated from live preview poc @dks333

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Note

Updates editor/live-preview.mdx to reflect the new cross-window live preview.

• Clarifies that live preview opens in a separate browser window, is local-only, and requires both editor and preview windows open with automatic syncing
• Updates comparison table Access to "Separate window (local only)" and adds upgrade path link for shareable preview deployments
• Changes toolbar button icon reference to media-play and updates instructions; adds note about auto-updating preview window
• Elevates authentication limitation to a Warning and polishes copy for real-time updates

^{Written by Cursor Bugbot for commit d11a340. This will update automatically on new commits. Configure here.}