A deb822 source using a keyring path or fingerprint in Signed-By currently enters the embedded-PGP-key state. Subsequent fields such as Suites and Components are then consumed as plain text instead of being highlighted.

Enter the PGP state only when its begin marker follows the field. Handle ordinary values, continuations and intervening comments separately, then return to the normal field rules. Add six regression cases and a changelog entry; the existing embedded-key golden sample remains unchanged.

Validation (Python 3.12, native Windows sandbox):

• Regression cases fail on the baseline (6 failures).
• Regression cases plus the embedded-key golden sample pass (7 tests); rerun on the final LF-normalized files.
• python -m tox -- -W error: 5336 passed, 16 skipped before normalizing the Windows checkout line endings to upstream LF; source text is otherwise identical.

AI assistance: prepared with OpenAI Codex and reviewed by a separate agent.