feat(ui): enhance typing screen with improved layout and real-time updates

[unhappychoice]

Summary

• Enhanced typing screen UI with improved layout and blue-based color theme
• Added real-time metrics updates during typing sessions
• Implemented line numbers display using actual source file line numbers
• Fixed critical CPM calculation bug during pause periods

Changes

UI Layout Improvements

• Replaced single outer border with individual section borders
• Applied consistent blue-based color scheme (cyan for Challenge, blue for Code, yellow for Metrics, green for Progress)
• Moved [ESC] Options to bottom-left corner without border for cleaner appearance
• Implemented compact layout with proper padding and spacing

Line Numbers Feature

• Added line numbers to code display using actual source file line numbers from Challenge data
• Current line highlighted in yellow with bold styling
• Other lines shown in dark gray for subtle appearance

Real-time Updates & CPM Fix

• Display updates every 100ms even without keyboard input
• Elapsed time, WPM, CPM, and other metrics now update in real-time
• FIXED: CPM no longer decreases during pause periods ([ESC] menu)
• Real-time metrics now use proper elapsed time calculation (excluding paused duration)
• Ensures consistency between real-time display and final results

Code Quality Improvements

• Simplified method signatures by removing unused parameters
• Refactored real-time calculation logic for better maintainability
• Eliminated duplicate code and improved consistency

Test plan

• All tests pass (cargo test) - 160 tests
• Code compiles without warnings (cargo check, cargo clippy)
• Code is properly formatted (cargo fmt)
• CPM calculation during pause periods verified
• Manual testing of typing screen layout and real-time updates
• Verify line numbers match actual source file line numbers
• Test UI responsiveness and color scheme

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 0% with 108 lines in your changes missing coverage. Please review.
✅ Project coverage is 32.76%. Comparing base (9087328) to head (141dbba).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
src/game/stage_renderer.rs	0.00%	101 Missing ⚠️
src/scoring/engine.rs	0.00%	4 Missing ⚠️
src/game/screens/typing_screen.rs	0.00%	3 Missing ⚠️

❌ Your patch status has failed because the patch coverage (0.00%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.
❌ Your project status has failed because the head coverage (32.76%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #143      +/-   ##
==========================================
- Coverage   33.00%   32.76%   -0.24%     
==========================================
  Files          83       83              
  Lines        9201     9268      +67     
==========================================
  Hits         3037     3037              
- Misses       6164     6231      +67     

Files with missing lines	Coverage Δ
src/game/screens/typing_screen.rs	0.00% <0.00%> (ø)
src/scoring/engine.rs	50.36% <0.00%> (ø)
src/game/stage_renderer.rs	0.00% <0.00%> (ø)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.