adventure: de-wrap transcript into flowing paragraphs

#23 in Riparion/riparion-retro — merged 2026-06-11

Problem

Long room descriptions in Colossal Cave showed the 1977 80-column teletype line breaks baked into advent.dat (rendered literally by white-space: pre-wrap), and consecutive messages had no spacing between them — so prose read like a fixed-width teletype instead of reflowing on a phone.

Change

Presentation-layer only; engine output is untouched.

• src/engine/text.rs — new reflow(s) (sibling to modernize, which is unchanged). Splits an output block into paragraphs on blank lines and joins wrap-residue lines back into flowing prose. The discriminator is line width (WRAP_THRESHOLD = 50): long lines were wrapped → rejoin with a space; short or indented lines were deliberate → keep the break. So:
  • room descriptions reflow to the viewport,
  • inventory lists stay one item per line,
  • centered dividers (- - -, --- POOF!! ---) keep their leading spaces.
• src/ui/components/transcript.rs — renders one <p class="t-out"> per paragraph (was one <p> per block) for visible paragraph spacing.
• assets/main.css — keeps pre-wrap (surviving list/divider breaks render; prose reflows), bumps bottom margin to 0.7rem.

Tests

cargo test -p adventure — all 28 pass, including the four walkthrough golden masters. Those compare content with whitespace normalized, so line-break changes are invisible to them; modernize's newline test is unaffected since modernize is unchanged. Added 4 unit tests for reflow (de-wrap, inventory, divider, paragraph split).

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