Dramatically improved the crate-level documentation to address feedback
that the API was too complex for newcomers to understand and integrate.

Key improvements:
✅ Progressive complexity examples (1 line → 2-3 lines → 3-5 lines → advanced)
✅ Clear entry points for different skill levels and use cases
✅ Comprehensive examples for each API tier
✅ Better discoverability of simplified APIs
✅ Enhanced module-level documentation

The documentation now provides a clear learning path from beginner
(SystemOverview::quick()) to expert (HardwareInfo::query()) with
domain-specific presets in between.

Published to crates.io with improved developer experience.