docs: conciseness review - cut filler, fix errors, remove duplicates

[datlechin]

Summary

• Cut 358 lines of filler, duplicate sections, and generic boilerplate across 22 doc files
• Fixed incorrect EXPLAIN ANALYZE guidance (was "avoid on slow queries", now correctly warns about production use)
• Added missing # Deep Links heading
• Deleted duplicate sections: Editor Zoom (keyboard-shortcuts), Terminal Usage (deep-links), Keyboard Shortcuts (er-diagram), Tips for Efficiency + Accessibility (keyboard-shortcuts)
• Cut ~40% of architecture.mdx (generic MVVM/SwiftUI/error handling examples replaced with concise table)
• Removed recommendation tables from editor-settings (font size, tab width)
• Removed marketing filler ("Best for...", "No more entering...", "at a glance")
• Split safe-mode trailing paragraph into proper NoSQL + Toolbar Badge sections
• Added Troubleshooting heading to icloud-sync

Test plan

• mint dev - verify all pages render correctly
• Check no broken internal links
• Spot-check 5+ pages for readability