Limit grid and export-preview cell text to 1000 UTF-16 code units plus an ellipsis. Edit large values in a wrapped dialog while preserving complete clipboard, export and database values.
Reproduced STATUS_STACK_OVERFLOW (0xC00000FD) in Windows WebView2 against a real PostgreSQL table with nine rows and 8.83 MB of jsonb data. Verified the fix through display, selection, editing, full clipboard copy, JSON file export and PostgreSQL writeback. All PR CI checks passed, including 5625 frontend tests and Rust checks on Windows, macOS and Linux.
Fixes#825
