[rupayon123]

A source file containing a standalone line continuation followed by a comment crashes the normalizer with AttributeError instead of returning diagnostics.

The continuation prefix creates an indentation node that may not occur in the previous indentation stack. Stop the comment walk at the root in that case. Also refresh the local node after a continuation is popped, so a trailing newline does not get an incorrect indentation warning.

Closes #219.

Validation on Python 3.12.13:

• The 18 new cases failed before the repair. They cover both EOF endings across the supported 3.6–3.14 grammar versions; the assertions check the expected diagnostic codes.
• Full test suite: 2,007 passed.
• Flake8 5.0.4 with the repository's CI command: passed.
• Zuban 0.5.1: no issues in 49 source files.
• git diff --check: passed.

Other Python runtime versions have not been run locally; grammar-version coverage is not the same as the CI runtime matrix.