Show Find and Replace in centered dialogs

[kisaraki]

Summary

Move Find and Replace from the rows above the document into centered modal dialogs.

Behavior

• keep the document viewport at its normal height while either dialog is open
• retain Enter, Ctrl+Alt+Enter, F3, and Escape behavior
• expose Find, Replace, Replace All, and Close as explicit dialog buttons
• place each search option on its own row so translated labels do not widen the dialog

Scope

This PR changes only the Find/Replace presentation and interaction in:

• crates/edit/src/bin/edit/draw_editor.rs
• crates/edit/src/bin/edit/main.rs

It does not include customized About content, version/authorship changes, copyright-header changes, themes, Markdown navigation, deployment scripts, or other features.

Validation

• cargo fmt --all -- --check
• Windows: cargo test -p edit --bin edit
• Windows: cargo build -p edit --release --locked
• Ubuntu 26.04 / WSL: cargo test -p edit --bin edit
• Ubuntu 26.04 / WSL: cargo build -p edit --release --locked

All commands completed successfully. Both release binaries report edit version 2.0.0.

Contribution

These changes are my original personal work, unrelated to any organization or company, and not created in the course of employment. I agree to contribute them under the Microsoft Contributor License Agreement and the project's MIT License.