Unwrap great-circle arc longitudes across the antimeridian so routes don't chord across the map (ISS-120)

CHANGELOG.md

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 # Changelog
 
+## v0.53.0 — 2026-09-22 14:47
+- **Antimeridian routes no longer chord across the map (ISS-120).** Routes whose great circle crosses ±180° (e.g. Auckland → Fua'amotu, Tonga) rendered as a line spanning the whole map: `greatCircleArc` sampled `positionAt`, which wraps every sample's longitude into [−180, 180], so consecutive samples jumped +179.x → −179.x and MapLibre — which draws LineStrings as-is with no ±180 splitting — connected them across the globe. New module-private `unwrapLons` in `lib/mapData.ts` re-expresses each arc's sample sequence in continuous longitudes (first sample keeps its raw lon; every later one is shifted by ±360 relative to the previous UNWRAPPED value until |Δlon| ≤ 180), applied inside `greatCircleArc` so all four line builders (`routesGeoJson`, `queuedRoutesGeoJson`, `hoverRouteGeoJson`, `hoverTraceGeoJson`) are fixed at once. One line stays one LineString — no splitting; out-of-range values render on MapLibre's adjacent world copies (`renderWorldCopies` is default-on). `queuedRoutesGeoJson` gets a second global pass after concatenation: each leg's arc unwraps relative to its OWN start airport, so at a joint the sequence can jump ±360 (leg 1 ends at dest+360k, leg 2 restarts at the raw dest) and the re-unwrap keeps multi-leg chains continuous. Non-crossing routes are byte-identical (no |Δlon| > 180 anywhere → the pass is a no-op).
+- **Tests.** Unit +4 in `lib/mapData.test.ts` (new "antimeridian crossing" block, real dataset pairs NZAA/NFTF/NZCH): eastward and westward crossings stay continuous (every consecutive |Δlon| < 180), endpoints exact mod 360 with the first sample still the raw origin, sampled chord length ≈ haversine within 1%, a non-crossing route's lons stay in [−180, 180], and a grounded plane's two-leg queue chain crossing ±180 stays continuous across the joint (the regression `queuedRoutesGeoJson`'s global pass guards). E2E +1 in `e2e/hover.spec.ts`: hovering an antimeridian-crossing package (hook-created NZAA → NFTF) draws one continuous trace — no rendered segment may contain a ±180 longitude jump; `expectHoverRoute`'s endpoint check now compares longitudes on the circle (mod 360, identical for any pair within ±180 so existing routes are unaffected) and `fitToAirports` unwraps crossing pairs so their bounds follow the short arc across the date line instead of spanning the wrong side of the globe.
+- **Known limitation (follow-up).** Plane MARKERS still use the snapshot's wrapped lat/lon (`lib/game/state.ts` → `positionAt`), so a plane mid-crossing teleports 360° on its marker at the instant it passes ±180 while its route line stays continuous. Fixing needs airport coordinates inside `planesGeoJson` (signature change + `Map.tsx` call site) — deliberately out of scope for this fix.
+
 ## v0.52.0 — 2026-09-22 10:45
 - **Fixed world clock, no player time controls (ISS-117).** The pause button and the 1×–1000× scale slider are gone from the left pane (`components/LeftPane.tsx`) — the world now always runs at a fixed `WORLD_TIME_SCALE = 24` (new client-safe `lib/worldClock.ts`, re-exported by the engine). The server advances time in a background tick: new `instrumentation.ts` starts `startBackgroundTick()` (1 s interval, singleton-guarded) under `NEXT_RUNTIME === 'nodejs'`, so the sim moves even with no open browser. **Idle-pause:** while no plane is flying or in repair the clock is frozen exactly — pure `shouldAdvanceTime(planes)` in `lib/sim/engine.ts` gates every tick (no catch-up jump on wake; `lastRealTickMs` still updates). Fresh worlds start at year 2000 (`STARTING_CLOCK_MS = Date.UTC(2000, 0, 1)` in `lib/game/seed.ts`; existing saves untouched — no migration). The client clock (`lib/useSimClock.ts`) extrapolates between polls at the fixed rate and freezes while idle, mirroring the server.
 - **API.** `POST /api/sim` deleted (route + OpenAPI entry; spec now lists twelve endpoints) and its controls removed from the engine (`applyTimeControls`, `clampTimeScale`, MIN/MAX_TIME_SCALE). The `/api/state` snapshot's `simState` is now `{ clockMs }` only — no `timeScale`/`paused`. New test-only hook `POST /api/test/set-timescale` behind the existing `FLIGHT_TEST_HOOKS=1` gate (sibling of `/api/test/set-health`, same 404-when-disabled convention): body `{ timeScale: finite number in [1, 100_000] }` else 400; ticks first under the sim lock and returns `{ clockMs, timeScale }`. The e2e suite's per-spec `setScale` helpers now call it (and verify from the response); every spec restores the world rate in `afterEach`.