fix: improve thread safety in tool registry

[github-actions]

This PR addresses remaining thread safety issues from the original PR #1182 that were NOT covered by the merged PRs #1175 and #1176.

Issues Fixed

1. Thread-unsafe tool registry access 🚨

Problem: Module-level functions remove_tool() and list_tools() bypassed thread-safe registry methods by directly accessing registry._tools and registry._functions dictionaries.

Solution:

• remove_tool() now uses registry.unregister() (uses internal locking)
• list_tools() now uses registry.list_tools() (uses internal locking)

2. Missing thread safety in registry singleton

Problem: get_registry() singleton creation lacked proper double-checked locking for concurrent initialization.

Solution: Added double-checked locking pattern with _registry_lock to prevent race conditions during singleton creation.

Code Changes

# BEFORE (NOT THREAD-SAFE):
def remove_tool(name: str) -> bool:
    registry = get_registry()
    if name in registry._tools:        # Direct access - race condition risk
        del registry._tools[name]
        return True
    # ...

# AFTER (THREAD-SAFE):  
def remove_tool(name: str) -> bool:
    return get_registry().unregister(name)  # Uses internal locking

Testing

• ✅ Basic syntax validation passes
• ✅ Thread-safe operations validated with test registration/removal
• ✅ No breaking changes to public API

Context

This addresses the remaining issues from PR #1182 that were identified by code reviewers (Qodo, CodeRabbit) but not covered by the merged thread safety fixes in PRs #1175 and #1176.

Compliance with AGENTS.md

• ✅ Protocol-driven: No heavy implementations added to core
• ✅ Backward compatible: No public API changes
• ✅ Performance: Minimal overhead, proper locking only where needed
• ✅ Multi-agent safe: Eliminates race conditions in tool registry
• ✅ DRY: Reuses existing thread-safe methods

Fixes remaining issues from #1167
Related to closed PR #1182

🤖 Generated with Claude Code