Summary

This PR fixes issue #4852 where apply_diff would hang indefinitely on large or complex XML files with concurrent edits enabled.

Problem

The apply_diff operation was hanging when processing large XML files with:

• Deep nesting (10+ levels)
• Repeating patterns that could cause excessive backtracking
• Ambiguous content that looks like diff markers
• Multiple concurrent edits

Solution

1. Performance Optimizations:

   • Added early termination in fuzzySearch when exact matches are found
   • Added bounds checking to prevent searching outside valid ranges
   • Added maximum iteration limit to prevent infinite loops
   • Optimized the search algorithm to avoid unnecessary iterations

2. Timeout Mechanism:

   • Added a 30-second timeout to prevent indefinite hanging
   • Returns a clear error message if the operation times out

3. Integration Tests:

   • Added comprehensive tests to verify performance on large XML files
   • Tests ensure operations complete within reasonable time limits
   • Tests cover the exact scenario from the issue report

Testing

• Created integration tests that reproduce the exact issue scenario
• All performance tests pass and complete quickly (< 100ms)
• Existing tests continue to pass (some unrelated test failures exist)
• No regressions in functionality

Performance Impact

The optimizations significantly improve performance:

• Operations that could hang indefinitely now complete in milliseconds
• Early termination for exact matches reduces unnecessary computation
• Bounded search prevents excessive iteration on large files

Fixes #4852