Similar to the search history (W31), the goto-line prompt now
keeps a history of recently-visited line numbers. Up/Down arrows
cycle through the history; Down past the newest entry clears
back to the live input.
- Editor::goto_history: Vec<u32> field (max 50 entries)
- Editor::goto_history_cursor: Option<usize> navigation position
- Editor::push_goto_history(line) / goto_history_up() /
goto_history_down() / reset_goto_history_cursor()
- GotoLine prompt commit pushes the line to history
- Up/Down arrows in the GotoLine prompt cycle through history
- push_goto_history skips consecutive duplicates
Added 2 unit tests covering: walk backwards/forwards, dedup.
Tests: 1399 pass (was 1397), zero warnings.
vasilito
0a16b05232