docs: humanize README — conversational tone, better structure

- Added "What is this?" section with real usage examples
- Added "Why use it?" comparison table (without vs with)
- Reorganized into narrative flow: what → why → install → capabilities → tools
- Companion skill section explains what it actually teaches (not just bullet points)
- Prompts section explains what each workflow does step by step
- Safety section adds "What happens" column for clarity
- Warmer tone throughout while keeping technical accuracy
- Collapsible sections for 69 additional tools

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: RandomSynergy17