Constant REFERENCE_ROUTES 

pub const REFERENCE_ROUTES: &[ReferenceRoute];

A spread of distances and difficulty; each entry tests something specific:

• the two short routes are the baseline case: lattice search only, at the low end of wall-clock time;
• the medium route sits between the short and long cases, still lattice-only, at real cross-gulf scale;
• “around Istria (moderate)” is a long case the lattice’s own margin escalation resolves without the visibility-graph fallback – worth checking if a future change makes it need that fallback;
• “around Istria (DEPARE-heavy)” is the hardest lattice-only case, exercising fetch_preferring_detail’s cost against dense DEPARE coverage; the most regression-sensitive figure in this list;
• Naples-Palermo, Bari-Brindisi, and Chioggia-Koper extend the geographic spread beyond the northern Adriatic, each a real, direct or near-direct route;
• Palermo-Olbia, Salerno-Napoli, and Marina di Campo (Elba)-La Spezia extend it further: open-sea crossings and short coastal hops;
• “La Maddalena to Porto Cervo” is short (about 10 NM) but tests the archipelago it crosses: dense small DEPARE tiles there make route_find::visibility::significant_shallow_areas’s own geo::unary_union slow if fetched over too wide an area, rather than the tight area find_route’s own margin schedule actually uses;
• “Licata to Catania” is the hardest included case: rounding Sicily’s Cape Passero requires the visibility-graph fallback’s basemap-derived corners, adaptive edge subdivision, and per-edge bisection together. Tens of seconds on a real chart, slower than every other case here; a future change that makes this meaningfully slower, or shifts the route’s shape away from hugging the cape, is worth noticing.