feat: Add Claude Code rules output format support and set up CLI for additional format support in the future

[poiley]

Overview

Implements Claude Code output format support by building a complete formatter architecture to replace the existing hardcoded Cursor format generation. This enables multi-IDE compatibility and extensible format support.

Technical Changes

New Formatter Architecture (rules_engine/formatters/)

Base Classes:

• BaseFormatter: Abstract base class defining formatter interface with convert(), save(), and get_info() methods
• FormatError: Custom exception class for formatter-specific errors

Concrete Implementations:

• CursorFormatter: Refactored existing logic into formatter class, maintains .cursor/rules/*.mdc output with YAML frontmatter
• ClaudeFormatter: New implementation generating CLAUDE.md with structured markdown sections

Management Layer:

• FormatManager: Registry pattern with formatter discovery, validation, and batch processing
• Plugin system foundation for third-party formatters via setuptools entry points

CLI Integration (rules_engine/cli.py)

Parameter Addition:

• Added --output-format/-o click option with choices: cursor, claude, all, comma-separated lists
• Format validation and error handling with descriptive messages
• Backward compatibility: defaults to cursor when not specified

Architecture Changes:

• Replaced inline format generation with FormatManager.convert_and_save()
• Removed _legacy_save_rules_with_format() function and fallback mechanisms
• Added _get_format_action_text() and _get_format_description() helpers for format-aware messaging
• Updated all user prompts to use appropriate terminology per selected format

Format Specifications

Cursor Format (existing, now formalized):

.cursor/rules/
├── rule-001.mdc
├── rule-002.mdc
└── ...

File structure:

title: "Rule Title"
tags: ["tag1", "tag2"]
priority: "high"

Rule content here...

Claude Format (new):

CLAUDE.md Project Rules

Rule: Rule Title

Priority: high | Tags: tag1, tag2

Rule content here...

Core Logic Changes (rules_engine/analyzer.py)

• Updated save_rules_with_format() to use new formatter architecture
• Enhanced error handling and progress reporting
• Maintained existing analysis pipeline while enabling multiple output formats

Usage

# Claude Code format (new)
rules-engine start -o claude /path/to/repo

# Cursor format (existing behavior)
rules-engine start -o cursor /path/to/repo
rules-engine start /path/to/repo  # default

# Multiple formats
rules-engine start -o cursor,claude /path/to/repo
rules-engine start -o all /path/to/repo