feat: add system locale display modes, mouse control for most functions

[woffko]

Summary

This PR adds system-locale display modes, consistent mouse navigation, and a cleaner control layout while preserving the existing Classic output and keyboard shortcuts.

Display modes

Added three persisted formatting modes:

• Classic — preserves the original CoMon formatting.
• System Compact — uses the operating system locale and compact K/M/B/T notation where appropriate.
• System Full — uses the operating system locale while keeping chart values expanded.

System formatting now applies consistently to:

• Numbers and separators
• Dates and times
• Month and weekday labels
• Usage and Activity charts
• Limits and reset dates
• Session History

Legacy system values in existing state files are restored as System Compact.

Token display improvements

• Clarified token pairs with the TOKENS (TOTAL / NON-CACHED) heading.
• Added locale-aware K/M/B/T abbreviations for large token values in System Compact mode.
• Added compact values inside vertical chart bars.
• System Full keeps chart values expanded.
• Classic output remains unchanged.

Mouse controls

Added direct mouse interaction throughout the TUI:

• Click the top tabs to switch between:
  • USAGE
  • ACTIVITY
  • LIMITS
  • HISTORY
• Usage controls:
  • TOKENS / TIME / RUNS
  • WEEK / MONTH
  • VERT / HORZ
• Activity controls:
  • TOKENS / TIME / RUNS
  • - / + project-count controls
• Click the footer on any screen to cycle the display mode.

Modal overlays block click-through to controls behind them.

UI cleanup

• Added aligned thin-border VIEW, GRAPH, and BARS panels to the Usage screen.
• Added matching VIEW and PROJECTS panels to the Activity screen.
• Added active-state styling to the current top navigation tab.
• Removed duplicate shortcut hints from screen headers.
• Kept the complete shortcut reference in the footer and Help overlay.
• Added compact fallbacks for narrow terminal windows.
• Preserved a minimum width for the workspace label before enabling framed controls.
• Fixed usage cards collapsing on short terminal windows.

Compatibility

• Existing keyboard shortcuts remain unchanged.
• Classic formatting remains unchanged.
• Existing state files remain compatible.
• No Kitty keyboard protocol changes or additional input dependencies are included.

Validation

• cargo test — 68 tests passed
• GitHub ASCII Check — passed
• PR is currently mergeable with no conflicts