fix(great-circle): fix antimeridian splitting by upgrading arc to v1.0.0

[thomas-hervey]

Summary

Fixes #3030

Details

Routes crossing the international dateline (e.g. Tokyo-LAX, Auckland-LAX, Shanghai-SFO) were returning a malformed MultiLineString with a gap at the +/-180 boundary. This was caused by a bug in the GDAL-ported linear heuristic in arc.js v0.1.x/v0.2.x.

Fix

arc v1.0.0 replaces the heuristic with analytical bisection, producing exact +/-180 boundary coordinates and a correctly closed MultiLineString.

Changes:

• Bump arc dependency from ^0.2.0 to ^1.0.0
• Remove offset from Arc() call. Antimeridian splitting is now automatic
• Mark options.offset as deprecated in JSDoc (kept for backward compat)
• Remove unused offset destructuring

Test

• Add three antimeridian test fixtures: Tokyo-LAX, Auckland-LAX, Shanghai-SFO
• Add tape tests asserting MultiLineString output and exact +/-180 boundary coords
• Fix fixture-dependent tests to use named getFixture() lookup instead of fixtures[0]
• Regenerate basic.geojson snapshot (arc@1.0.0 defaults to 100 points)

When testing locally, arc@0.2.0 fails, but passes at arc@1.0.0

=== arc@0.2.0 ===
FAIL  Tokyo -> LAX: expected MultiLineString, got LineString
FAIL  Auckland -> LAX: gap at split -- last=[174.7900,-36.8500] first=[-176.0046,-29.7388]
FAIL  Shanghai -> SFO: expected MultiLineString, got LineString

found 0 vulnerabilities
=== arc@1.0.0 ===
PASS  Tokyo -> LAX: split at antimeridian, lat=47.3643
PASS  Auckland -> LAX: split at antimeridian, lat=-33.0522
PASS  Shanghai -> SFO: split at antimeridian, lat=52.3090
[rerun: b3]

... and the visual results were verified in geojson.io (see screenshot below)

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[thomas-hervey]

@smallsaucepan @rowanwins I see that you've contributed more recently and was wondering if I could get your review on this PR. In short, it's a bump of the arc package to resolve an antimeridian splitting issue #3030 .

Thanks!

[smallsaucepan]

Thanks for this. While checking to see if this might fix the sourcemap issue #2721 as well noticed that arc as of 1.0.0 is ESM only?