- Introduce `IconMode` in core config (default Auto) and bump schema version to 1.4.0.
- Add `FileIconSet`, `IconDetection`, and `FileIconResolver` to resolve per‑file icons with configurable fallbacks and environment variable `OWLEN_TUI_ICONS`.
- Export resolver types from `owlen-tui::state::file_icons`.
- Extend `ChatApp` with `file_icons` field, initialize it from config, and expose via `file_icons()` accessor.
- Append system status line showing selected icon set and detection source.
- Implement breadcrumb construction (`repo > path > file`) and display in code pane headers.
- Render icons in file tree, handle unsaved file markers, hidden files, and Git decorations with proper styling.
- Add helper `collect_unsaved_relative_paths` and tree line computation for visual guides.
- Provide `Workspace::panes()` iterator for unsaved tracking.
- Update UI imports and tests to cover new breadcrumb feature.