fix: prevent false positive test file detection for projects in /tests/ folders

When a project is located inside a directory named "tests" (e.g.,
/home/user/tests/myproject), source files were incorrectly filtered
as test files because the full path contained "/tests/".

The fix ensures directory pattern matching (/test/, /tests/, /__tests__/)
only applies to the relative path from project root, not parent directories.
If the relative path cannot be computed, we now skip directory pattern
matching entirely instead of checking the full path.

Example:
- Before: /home/user/tests/myproject/src/utils.ts was filtered as test file
- After: Only checks if /src/utils.ts contains /tests/ (correctly returns false)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Saga4

codeflash/discovery/functions_to_optimize.py

@@ -839,11 +839,13 @@ def is_test_file(file_path_normalized: str) -> bool:
             if any(pattern in file_lower for pattern in test_file_name_patterns):
                 return True
             # Check directory patterns, but only within the project root
-            # to avoid false positives from parent directories
-            relative_path = file_lower
+            # to avoid false positives from parent directories (e.g., project at /home/user/tests/myproject)
             if project_root_str and file_lower.startswith(project_root_str.lower()):
                 relative_path = file_lower[len(project_root_str) :]
-            return any(pattern in relative_path for pattern in test_dir_patterns)
+                return any(pattern in relative_path for pattern in test_dir_patterns)
+            # If we can't compute relative path from project root, don't check directory patterns
+            # This avoids false positives when project is inside a folder named "tests"
+            return False
         # Use directory-based filtering when tests are in a separate directory
         return file_path_normalized.startswith(tests_root_str + os.sep)