fix: indent profile continuation lines 💚

[kingrubic]

Summary

• render multiline profile bodies as indented Markdown continuation lines
• share the renderer between precomputed and first-run digest paths
• add regression coverage for a multiline Stack profile

Closes #74

Testing

• npm run check (30 files, 298 tests passed)

AI assistance

AI tooling assisted with the implementation; I reviewed and understand the submitted changes.

[kingrubic]

Closing this PR to tidy the backlog after more than 48 hours without maintainer feedback. Please feel free to reopen it if a maintainer finds the contribution useful. Thank you.