[dmoliveira]

Summary

• move prompt editor state and prompt history load/save helpers from src/main.rs into src/prompt_editor.rs
• preserve prompt editor behavior and history persistence contracts while reducing another high-churn chunk in src/main.rs
• keep the extracted code covered by existing prompt editor and history tests with strict clippy enforcement

Validation

• cargo test
• cargo clippy --all-targets --all-features -- -D warnings