### Added
- ExtensionAPI: `setModel()`, `getThinkingLevel()`, `setThinkingLevel()` methods for extensions to change model and thinking level at runtime ([#509](https://github.com/badlogic/pi-mono/issues/509))
- Exported truncation utilities for custom tools: `truncateHead`, `truncateTail`, `truncateLine`, `formatSize`, `DEFAULT_MAX_BYTES`, `DEFAULT_MAX_LINES`, `TruncationOptions`, `TruncationResult`
- New example `truncated-tool.ts` demonstrating proper output truncation with custom rendering for extensions
- New example `preset.ts` demonstrating preset configurations with model/thinking/tools switching ([#347](https://github.com/badlogic/pi-mono/issues/347))
- Documentation for output truncation best practices in `docs/extensions.md`
- Exported all UI components for extensions: `ArminComponent`, `AssistantMessageComponent`, `BashExecutionComponent`, `BorderedLoader`, `BranchSummaryMessageComponent`, `CompactionSummaryMessageComponent`, `CustomEditor`, `CustomMessageComponent`, `DynamicBorder`, `ExtensionEditorComponent`, `ExtensionInputComponent`, `ExtensionSelectorComponent`, `FooterComponent`, `LoginDialogComponent`, `ModelSelectorComponent`, `OAuthSelectorComponent`, `SessionSelectorComponent`, `SettingsSelectorComponent`, `ShowImagesSelectorComponent`, `ThemeSelectorComponent`, `ThinkingSelectorComponent`, `ToolExecutionComponent`, `TreeSelectorComponent`, `UserMessageComponent`, `UserMessageSelectorComponent`, plus utilities `renderDiff`, `truncateToVisualLines`
- `docs/tui.md`: Common Patterns section with copy-paste code for SelectList, BorderedLoader, SettingsList, setStatus, setWidget, setFooter
- `docs/tui.md`: Key Rules section documenting critical patterns for extension UI development
- `docs/extensions.md`: Exhaustive example links for all ExtensionAPI methods and events
- System prompt now references `docs/tui.md` for TUI component development