Address PR feedback + fix typos

Author: zastrowm

src/strands/_exception_notes.py

@@ -1,15 +1,13 @@
 """Exception note utilities for Python 3.10+ compatibility."""
 
-import sys
-
-# add_note was add_note in 3.11 - we hoist to a constant for facilitate testing
-supports_add_note = sys.version_info >= (3, 11)
+# add_note was added in 3.11 - we hoist to a constant to facilitate testing
+supports_add_note = hasattr(Exception, "add_note")
 
 
 def add_exception_note(exception: Exception, note: str) -> None:
     """Add a note to an exception, compatible with Python 3.10+.
 
-    Uses add_note() in Python 3.11+ or modifies the exception message in Python 3.10.
+    Uses add_note() if it's available (Python 3.11+) or modifies the exception message if it is not.
     """
     if supports_add_note:
         # we ignore the mypy error because the version-check for add_note is extracted into a constant up above and