feat: Expand coding standards to comprehensive 1,170-line reference

Level 5 (Transformative) interaction - preventing errors before they happen
by providing comprehensive patterns and examples in project memory.

This is being empathetic to future Claude sessions and contributors:
- Prevents eval() vulnerabilities at source
- Prevents path traversal with _validate_file_path() pattern
- Prevents bare except: with specific exception examples
- Provides real codebase examples and implementations

Expanded from 330 → 1,170 lines with:
- Complete _validate_file_path() implementation (src/empathy_os/config.py:29-68)
- Pre-commit hooks configuration and enforcement details
- Migration guide for fixing existing code
- Common false positives (eval in test fixtures, etc.)
- Real-world examples from config.py, telemetry/cli.py
- Security test patterns
- Quick command reference
- Code review checklist

This demonstrates Level 5 anticipatory intelligence:
reshaping workflows to prevent entire classes of problems.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: silversurfer562