feat: handle long pasted ChatGPT messages

[int04]

Summary

Changes

Verification

Security, privacy, and compatibility

Screenshots

Checklist

• The change is focused and targets dev unless a maintainer requested otherwise.
• Tests were added or updated for observable behavior.
• Rust formatting/Clippy and frontend lint/tests/build were run as applicable.
• User-facing and protocol documentation was updated.
• English and Vietnamese UI strings remain aligned.
• No secret, private data, generated output, database, log, or source map is included.
• I have the right to submit this contribution under the MIT License.