kaintuck: faro & vingt-et-un card tables Under-the-Hill

#52 in Riparion/riparion-retro — merged 2026-06-15

Wires the two new minigames-kit card games into Natchez Under-the-Hill, replacing the single timing-wheel gamble with a faro bank and a vingt-et-un table (RESEARCH_GAMBLING).

Behaviour

• Two new Natchez menu options ("Sit in on the faro bank", "Take a hand of vingt-et-un") in place of "Spend a night Under-the-Hill".
• Existing escrow model: buy in (your chips), play a full session, rise with whatever chips remain — net swing applied to cash, small reputation bump on a winning night.
• Decks vary per sit-down (encounter_seed mixes in live cash).

Wiring

• trail-kit: Faro/VingtUn MiniParams variants (static table knobs; stake/target derive from the live buy-in).
• kaintuck-engine: CardTask + MiniTask::Card, Mode::Faro/VingtUn, play_faro/play_vingt_un escrow launchers, hand-coded economic resolves (engine stays kit-free, takes primitives).
• kaintuck.ron: two minigame entries + the two menu options.
• kaintuck UI: enable faro/vingt_un kit features, route modes to the generic Minigame host, swap the Natchez buy-in flow.

Notes

• The engine gamble() / Action::Gamble is kept: the autonomous-economy bots gamble through it and it's pinned by golden_trace_is_stable. Only the player-facing path changed.
• Patch versions bumped: trail-kit 0.1.14, kaintuck-engine 0.1.4, kaintuck 0.1.24.
• All 77 engine tests pass (incl. golden trace + scenario consistency); full workspace builds.

🤖 Generated with Claude Code