perf: Optimize stack view rendering and add LRU cache with data-driven config

[mhiro2]

Summary

• Improve performance with LRU cache for realpath and O(1) popup lookups
• Optimize stack view to render only changed lines
• Refactor config validation to be data-driven

Changes

• 9525fc9 : perf(location): bound realpath cache with LRU and reset
  • Implement LRU cache with configurable max size for realpath resolution
  • Add realpath_cache_max_size config option and cache reset functionality
• 6ba5179 : refactor(config): make validation data-driven
  • Convert validation logic to table-driven approach for better maintainability
  • Add emmylua annotations for validation rules
• ffd1e88 : perf(stack): add O(1) popup lookup indexes
  • Add popup_id_to_item and location_to_popup indexes for constant-time lookups
  • Expose get_popup_by_location() API for direct popup access
• 29aa6f5 : chore(lint): fix shadowed local and apply formatting
• bbcba06 : perf(stack-view): render only changed lines
  • Implement diff-based rendering to update only modified lines
  • Add render state tracking to minimize buffer updates
• 1df2325 : fix(config): fallback invalid ui.path.max_width type
  • Gracefully handle invalid max_width values by falling back to default