Thinking selector fix:
- Replace hardcoded 50-character borders with DynamicBorder component
that adjusts to viewport width
- Prevents crash when terminal is resized narrow
Text/Markdown rendering fixes:
- Fix Markdown wrapSingleLine to check if adding next character would
exceed width BEFORE adding it (was checking AFTER, causing lines to
be 1 character too long)
- Add word truncation in Text component for words longer than
contentWidth (prevents long unbreakable words from exceeding width)
These fixes prevent "Rendered line exceeds terminal width" errors.
- Create UserMessageComponent - handles user messages with spacing
- Create AssistantMessageComponent - handles complete assistant messages
- Create ThinkingSelectorComponent - wraps selector with borders
- Add setSelectedIndex to SelectList for preselecting current level
- Simplify tui-renderer by using dedicated components
- Much cleaner architecture - each message type is now a component
