EditBox caret keys, selection and focus blink follow 1.12.1 (#750)

Several EditBox keys differed from 1.12.1:
- Up/Down did nothing in a multi-line box;
- Home/End went to the text's ends;
- `HighlightText` and Ctrl+A moved the caret;
- focus did not restart the blink;
- a non-digit kept a numeric box's selection;
- Option+Up could not recall chat history on a Mac.

In 1.12.1, Up/Down move a wrapped row, keeping the letter column (`0x77cb20`), or recall history in a single-line box with any modifier but Shift. Home/End stop at a newline (`0x77c980`, `0x77c9f0`). `HighlightText` writes only the selection (`0x77cca0`), and Shift extends by `0x77cd10`. Focus restarts the blink (`0x77dd68`), and Insert deletes the selection before its digit test (`0x77bf41`).

benilla now does each. Down onto the last row lands at the end, and history stays shell-style, both deviations.

Tests cover each key, in the engine and the stock mail and ticket boxes.

Fixes #735
Fixes #736
Fixes #737
Fixes #738
Fixes #745
Fixes #747

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/benilla-app/src/ui_script/input.rs

@@ -285,7 +285,7 @@ pub(super) fn feed_ui_input(
             }
         } else if let Some(chord) = chord {
             // The gate is on the key, not the action: a gated arrow never reaches the box (the
-            // reference's `return 0`), while HOME/END, which also make `Move { unit: Edge }`, do.
+            // reference's `return 0`), while HOME/END, which also make a `Move`, do.
             let gated_arrow = capture.arrows_fall_through
                 && matches!(
                     ev.key_code,