fix(think): implement automatic recursion prevention for think tool

[cagataycali]

Description

This PR implements automatic recursion prevention for the think tool to resolve a critical bug where nested agents could call the think tool recursively, causing infinite loops and stack overflow errors.

Problem

The think tool was vulnerable to infinite recursion when:

• Nested agents inherited all tools from their parent (including the think tool itself)
• Tools were explicitly specified and included the think tool
• Multi-cycle thinking operations created nested agents that could call think again

This created a dangerous recursion pattern: think → nested agent → think → nested agent → ∞

Solution

Implemented automatic exclusion of the think tool from nested agents with:

• Smart filtering: Automatically removes think tool from nested agent tool lists
• Comprehensive logging: Warning messages for explicit requests, debug messages for inheritance scenarios
• Backward compatibility: All other tools remain available, no breaking changes to existing functionality
• Multiple scenario handling: Works for explicit tool requests, tool inheritance, and edge cases

Key Changes

• Core Logic: Modified tool filtering in think.py to exclude think tool from nested agents
• System Prompts: Updated prompts to encourage use of other tools instead of prohibiting recursion
• Logging: Added appropriate warning/debug messages for recursion prevention tracking
• Comprehensive Testing: Added 5 new test cases covering all recursion scenarios:
  • Explicit tool requests including think
  • Tool inheritance from parent agents
  • Edge case with only think tool requested
  • Multi-cycle operations with recursion prevention
  • Various tool filtering combinations

Related Issues

Fixes infinite recursion bug in think tool that could cause stack overflow and system instability.

Documentation PR

No documentation changes required - this is an internal bug fix that maintains existing API compatibility.

Type of Change

• Bug fix
• New Tool
• Breaking change
• Other (please describe):

Testing

Comprehensive testing completed with all quality assurance checks passing:

Pre-commit Hooks (All Passed ✅)

• hatch fmt --linter - ✅ Passed
• hatch fmt --formatter - ✅ Passed
• Type linting - ✅ Passed
• Unit tests - ✅ Passed
• Commit message validation - ✅ Passed

Additional Testing

• New Test Coverage: Added 5 comprehensive test cases covering all recursion scenarios
• Edge Case Testing: Verified behavior with empty tool lists, single tool requests, multi-cycle operations
• Integration Testing: Tested with actual think tool usage to ensure no functional regression
• Logging Verification: Confirmed appropriate warning/debug messages are generated
• Backward Compatibility: Verified existing think tool functionality remains unchanged

Checklist

• I have read the CONTRIBUTING document
• I have added tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature
• My changes generate no new warnings
• Any dependent changes have been merged and published

Test Results Summary

fix(think): implement automatic recursion prevention for think tool
✅ Format code: Passed
✅ Lint code: Passed  
✅ Type linting: Passed
✅ Unit tests: Passed (including 5 new recursion prevention tests)
✅ Check commit message: Passed

Before/After Behavior

Before (Problematic):

# This would cause infinite recursion
think_tool(thought="analyze this", tools=["think", "calculator"])
# Result: Stack overflow due to think → nested agent → think → ...

After (Fixed):

# Same call now safely excludes think tool from nested agent
think_tool(thought="analyze this", tools=["think", "calculator"])
# Result: Nested agent gets only ["calculator"], recursion prevented
# Warning logged: "Excluding 'think' tool from nested agent to prevent recursion"

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