[Feature] Add detect_cycles MCP Tool for Circular Dependency Detection

[VooDisss]

Summary

Implement a new MCP tool detect_cycles that identifies circular dependencies in codebases using the RPG dependency graph.

Motivation

Circular dependencies are architectural smells that:

• Prevent independent compilation, testing, and reuse
• Cause changes to ripple through the entire cycle
• Make refactoring risky and expensive

Currently, the RPG system provides dependency graphs but lacks a dedicated tool to detect and report circular dependencies. Users need a way to:

1. Identify cycles in their codebase
2. Understand which areas/files are affected
3. Filter to specific areas or cross-file/cross-area cycles

Proposed Solution

Add a new detect_cycles MCP tool with:

Core Functionality

• Detect circular dependencies using DFS algorithm
• Report statistics: total cycles, entities involved, files affected
• Break down by hierarchy area
• Filter by area, cycle length, cross-file, cross-area

Output Format

Use TOON-optimized format for LLM efficiency:

• Summary with inline objects
• Tabular area breakdown
• Compact cycle representation with file:entity chains

Funnel Design

• First call returns summary + recommendations
• Agent calls again with filters for details
• Guides LLM on next steps

Parameters

Parameter	Type	Description
area	string	Filter to hierarchy area(s)
max_cycles	number	Limit results
min_cycle_length	number	Skip trivial 2-cycles
cross_file_only	boolean	Only cross-file cycles
cross_area_only	boolean	Only cross-area cycles
sort_by	string	Sort by length/file_count
include_files	boolean	Include file paths
ignore_rpgignore	boolean	Include ignored files

Example Output

cycles: {total: 512, entities: 467, files: 46, areas: 8, cross_file: 152}

area_breakdown[8]{area,cycles,len2,len3,len4+,files}:
  Navigation,45,20,15,10,8
  Parser,38,12,14,12,6

next_step: Use area/max_cycles/cross_file_only to filter

Acceptance Criteria

• Tool detects circular dependencies in RPG graph
• Outputs TOON-optimized format
• Supports area, length, cross-file, cross-area filtering
• Provides summary with recommendations (funnel design)
• Respects .rpgignore patterns
• Includes unit tests for all filter paths
• Documented in server_instructions.md

[VooDisss]

@userFRM implemented the feature in #61 . Please check and merge, thanks!

[VooDisss]

Merged, thank you, @userFRM !