Editor text wrapping now uses grapheme-aware width calculation instead
of string length. Fixes crash when pasting text containing emojis like
✅ or CJK characters that are 2 terminal columns wide.
Browse previously submitted prompts using Up/Down arrow keys, similar to
shell history and Claude Code's prompt history feature.
- Up arrow when editor is empty: browse to older prompts
- Down arrow when browsing: return to newer prompts or clear editor
- Cursor movement within multi-line history entries supported
- History is session-scoped, stores up to 100 entries
- Consecutive duplicates are not added to history
Includes 15 new tests for history navigation behavior.
