The test proved that normalizing only in tests is not sufficient.
The production code must use forward slashes to:
1. Prevent escape sequence issues (\a, \t interpreted as bell, tab)
2. Ensure consistent behavior across platforms
3. Allow portable Taskfiles that work on all OSes
Use filepath.ToSlash() for ROOT_DIR, ROOT_TASKFILE, USER_WORKING_DIR,
TASK_DIR, TASKFILE, and TASKFILE_DIR to ensure consistent forward
slashes across platforms.
This fixes an issue on Windows where backslashes in paths were being
interpreted as escape sequences when used in shell commands like
`echo {{.ROOT_DIR}}`.
