Great-circle vs rhumb-line passage plan with ETAs

# Great-circle vs rhumb-line passage plan with ETAs `input.json` (synthetic; not for navigation): `waypoints` ([lat, lon] decimal degrees, legs may cross the 180° meridian), `speed_kn`, `depart_utc` ("YYYY-MM-DDTHH:MM:SSZ"). Write `solve.py` (Python 3 standard library only); `python solve.py input.json answer.json` writes `answer.json` and `route.svg`. Fresh inputs are used too. ## Rules (sphere, R = 3440.065 nm) - Longitude difference dlon is always wrapped into [-180°, 180°). - **Great circle**: haversine distance; initial course = atan2(sin dlon * cos lat2, cos lat1 * sin lat2 - sin lat1 * cos lat2 * cos dlon) mod 360. - **Rhumb line**: dpsi = ln(tan(pi/4 + lat2/2) / tan(pi/4 + lat1/2)); q = dlat / dpsi, or cos(lat1) when |dpsi| <= 1e-12; distance = sqrt(dlat^2 + q^2 * dlon^2) * R (radians); course = atan2(dlon, dpsi) mod 360. - The boat sails the **rhumb** legs at `speed_kn`; leg ETA = departure + cumulative rhumb distance / speed, rounded to the nearest minute (half a minute rounds up), formatted "YYYY-MM-DDTHH:MMZ". - `rhumb_extra_pct` = (total rhumb - total GC) / total GC * 100. Round distances to 2 decimals, courses to 1, the percentage to 3. ## Visual output: route.svg Static, self-contained SVG (root `<svg>`, no scripts, images, links or external assets; renders headless) with `<polyline id="route-gc">`, `<polyline id="route-rhumb">` and an element `id="waypoints"`. The drawing (projection etc.) is not graded. ## answer.json `{"legs": [{"gc_nm", "gc_initial_course", "rhumb_nm", "rhumb_course", "eta_utc"}, ...], "total_gc_nm", "total_rhumb_nm", "rhumb_extra_pct", "arrival_utc"}` ## Scoring Hidden checks (partial credit; all must pass): `great_circle_legs`, `rhumb_legs` (first four legs; distances within 0.011, courses within 0.11), `totals`, `etas` (exact strings), `route_svg_static` (route.svg exists, follows the static rules, has the ids/tags above), `fresh_run_1`, `fresh_run_2` (all keys, within 0.02). 60-second limit per run.