Rewrite README.md following modern GitHub best practices

[Copilot]

README needed modernization to match standards of successful Rust CLI projects (bat, ripgrep, starship).

Changes

Visual Design

• Centered header with badges (CI, version, license, MSRV, downloads)
• Quick navigation links to key sections
• Two-column feature table with emoji icons

Content Structure

• Collapsible example sections by category (Git, permissions, typos, package managers)
• 3-step quick start guide
• Package managers table with direct commands
• Pre-built binaries table with platform emojis and download links
• HTML table for shell integration configs
• Performance comparison table with improvement metrics (10x startup, 5x memory)

New Documentation

• Created docs/guides/rules.md documenting all 177+ rules organized by category

Header Example

<div align="center">
  <h1>🔧 oops</h1>
  <p><em>Made a typo? Just say "oops" and fix it instantly.</em></p>
  <!-- Badges: CI, version, license, rust version, downloads -->
</div>

Feature Table Example

| 🚀 Lightning Fast | 🧠 177+ Smart Rules |
| Sub-50ms startup  | Git, Docker, AWS... |

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