Add guidance: prefer CaptainHook over GrumPHP for pre-commit hooks

[CybotTM]

Proposed Addition

Add guidance to prefer CaptainHook over GrumPHP for code style enforcement:

• Use ONE authoritative code style tool, not multiple conflicting ones
• Prefer CaptainHook over GrumPHP for pre-commit hooks
• Use PHP-CS-Fixer with @PER-CS as the single source of truth
• PSR-2 is deprecated - use PSR-12/PER-CS

Context

GrumPHP and PHP-CS-Fixer can have conflicting rules (e.g., single_line_empty_body). Having a single source of truth avoids these conflicts.

Suggested Location

references/static-analysis-tools.md or references/psr-per-compliance.md