Replace Regex with findnext for occurrence counting

- Use findnext in a loop instead of eachmatch(Regex(...))
- More efficient and avoids regex escaping complexities
- Same functionality with simpler, more direct approach
- Tested with various patterns to ensure correctness

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Keno

src/tools/str_replace_editor.jl

@@ -199,8 +199,17 @@ function execute(tool::StrReplaceEditorTool, params::Dict)
                 return create_content_response("Error: String not found in file", is_error=true)
             end
 
-            # Count occurrences
-            occurrences = length(collect(eachmatch(Regex(escape_string(old_str)), content)))
+            # Count occurrences using findnext
+            occurrences = 0
+            pos = 1
+            while true
+                range = findnext(old_str, content, pos)
+                if isnothing(range)
+                    break
+                end
+                occurrences += 1
+                pos = last(range) + 1
+            end
 
             # Replace the string
             new_content = replace(content, old_str => new_str)