- Move 20 shell scripts to integration_tests/test_scripts/
- Move 14 CSV test files to integration_tests/test_data/
- Move 34 Rust test files to integration_tests/
- Update README with new directory structure
- Clean up main directory from test clutter

This keeps the project root clean and organizes tests logically.

- F6 now only shows DataTable conversion, doesn't switch to PrettyQuery
- F7 now shows Pretty Query view (moved from F6)
- Status message shows memory comparison: 'JSON ~XKB vs DataTable ~YKB'
- Debug logs show column type details when RUST_LOG=debug

The status message was being immediately overwritten by PrettyQuery mode.

- F6 was only handled in Command mode, not Results mode
- Added F6 handler to handle_results_input() function
- Now pressing F6 in Results mode will show DataTable conversion
- Status message displays memory comparison in status bar

The demo now works correctly from Results view where users spend most time.

- DataTable now counts actual string content, not just enum size
- JSON size calculation includes field name duplication overhead
- More accurate memory comparison for real-world data

For 10k rows with 53 columns, the estimates should now be more realistic,
showing actual memory usage including string content and overhead.