change inactive tab text from gray1 to text_dim for better contrast

- replace silent error discarding with eprintln logging
- remove .expect() panics in favor of .unwrap_or_else() with fallbacks
- improve error visibility in data loading
- use .and_then() instead of nested .unwrap() for cleaner code

fixes identified in code review against CLAUDE.md guidelines:
- main.rs:224,227 - pane operations now log failures
- view.rs:102 - config_dir uses fallback instead of panic
- main.rs:61-80 - data loading now logs parse/read errors
- consolidate_channels.rs:67-78 - timestamp conversion cleaner

Each tab now has × button to remove view from panel's stack.
PaneContent.remove_view() handles index adjustment when closing.

Views are now the universal abstraction:
- Panel.view_stack holds multiple view IDs
- Panel.active_view tracks which is showing
- View.filter enables channel-specific filtering
- Click channel → creates View::channel_tracks() → adds to panel

This creates foundation for:
- Tab-based view switching per panel
- AI-generated views ("show channels by title")
- User-created views via TOML files

The flow: user clicks channel → dynamic view created/found in global
registry → pushed to panel's stack → panel renders filtered tracks