[lesnik512]

Summary

• Scrub message-less structlog records rendered by lite-bootstrap before sending them as Sentry issues or breadcrumbs. Use [No message] as the Sentry message.
• Keep the original stdout JSON. Independently configured JSON renderers do not carry the record marker, so their message-less records remain outside this fix.

Refs #450.

Verification

• Confirmed the new envelope test fails on the password leak before the fix.
• just test-ci passed with 666 tests and 100% line coverage.
• Type and lint checks passed. The envelope regression also passed with sentry-sdk 2.70.0 and structlog 21.3.0.