Preserve deeply indented lines after TUI list items

[brownie-ricon]

Summary

• keep shallow hanging-indent continuations folded into list items
• preserve deeper indented lines after list items as literal markdown-ish lines instead of collapsing them into bullet prose
• add a renderer regression test and refresh generated README test count

Validation

• mise run test
• mise run readme -- --check
• mise exec -- codebase lint