Docs: Implement CLAUDE.md best practices with modular structure

[nek0der]

Description

This PR implements official Claude Code best practices for CLAUDE.md files, optimizing for the 150-200 instruction limit and enabling team collaboration through modular structure.

Key changes:

• Refactored CLAUDE.md from 137 to 73 lines (47% reduction)
• Created .claude/rules/ directory for progressive disclosure pattern
• Split detailed workflows into separate rule files (pr-workflow.md, security.md, testing.md)
• Updated .gitignore to properly handle team-shared vs personal settings
• Fixed incorrect CLI repository link
• Unified all documentation to English

This follows the "prefer pointers to copies" principle and reduces cognitive load by loading detailed rules only when needed.

Related Issue

N/A

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)
• Build/CI changes

How Has This Been Tested?

This change affects documentation only, no code changes.

Verification performed:

• Reviewed all created files for accuracy and completeness

• Verified .gitignore correctly excludes .claude/*.local.* files

• Confirmed .claude/settings.local.json is properly ignored

• Validated all file references and links are correct

• Ensured all content is in English

• Manual testing on Windows x64

• Manual testing on Windows ARM64

• Tested with multiple providers (list which ones)

Test Configuration:

• Windows Version: N/A (documentation only)
• .NET Version: N/A (documentation only)

Screenshots (if applicable)

N/A - Documentation changes only

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly
• I have added entries to CHANGELOG.md (if applicable)
• My changes generate no new warnings
• I have tested my changes locally
• Any dependent changes have been merged and published

Breaking Changes

N/A

Additional Notes

Files changed:

• CLAUDE.md - Reduced from 137 to 73 lines, now references modular rule files
• .claude/rules/pr-workflow.md - PR validation checklist and creation process
• .claude/rules/security.md - Security rules (provider validation, secrets, GPL)
• .claude/rules/testing.md - Testing requirements and naming conventions
• .gitignore - Changed from ignoring entire .claude/ to only personal settings

Benefits:

• 47% reduction in main CLAUDE.md file
• ~38% reduction in instruction count (40+ → ~25 in main file)
• Better separation of concerns (universal context vs task-specific workflows)
• Team can share rules via git while maintaining personal settings locally
• Follows official Claude Code best practices for 2026

References:

• Claude Code: Best practices for agentic coding
• The Complete Guide to CLAUDE.md
• Claude Code settings documentation