Add Fort Nash, an Oregon Trail-engine game

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

What

Adds Fort Nash (games/fort-nash/), a new game built by re-skinning the oregon-trail engine: James Robertson's 1779 overland march down the Wilderness Road — Fort Patrick Henry (Kingsport) → Cumberland Gap → the French Lick, where the party raised Fort Nashborough on Christmas Day, 1779.

It reuses the whole proven turn-flow, all seven minigames, scoring, save/resume, and the build-time cover lookup — re-themed to the 1779 frontier.

Highlights

• 9 historical checkpoints replace the Oregon landmarks (Terrain enum + mile bands); weekly turns replace fortnights (Nov 1 – Dec 27, 1779).
• Signature ice crossing — the frozen Cumberland on Christmas Day is a scripted one-time steady-hands trace; a badly shaky run cracks the ice (GameOverCause::IceBroke).
• Re-themed events: Cherokee/Chickamauga war party, outlaws/wolves, freezing sleet, frostbite first-aid, Powell Mountain & Cumberland Gap passes; frontier ranks and retuned scoring. Tuned numeric logic and field identifiers kept to minimize risk.
• All 20 UI screens + status bar re-themed; new log-stockade icon set; README, FORTNASH_IMAGE_KEYS.md, fort-nash storage keys. Ships with no cover art — the build auto-indexes whatever is present and falls back cleanly.
• justfile: every dx serve recipe now passes --debug-symbols=false (not just build), so serving stops spewing the binaryen/DWARF wasm-opt SIGABRT.

Verification

• cargo test -p fort-nash — 49/49 pass (multi-seed full journeys, every minigame, the ice-crack death, win path, cover-key resolution).
• cargo clippy -p fort-nash --all-targets — clean.
• dx build --release --debug-symbols false and dx serve --release — build, bundle, and launch with no wasm-opt abort.

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