Implement line2points in mapbrowser.js

[Copilot]

line2points was a stub (/* TBD */) with no implementation.

Changes

• Geodesic interpolation: computes initial bearing via haversine formula, then uses ol.sphere.offset to place points at exact meter intervals along the great-circle arc — avoids the distortion of linear lon/lat interpolation
• Distance calculation: uses ol.sphere.getDistance for the total arc length between endpoints
• Edge cases: returns [] for invalid/non-positive distance, [from] when from === to
• Endpoint inclusion: uses Math.ceil + Math.min clamp so both from and to are always included without duplicates regardless of divisibility

// Returns [lon,lat] points spaced ~500m apart along the geodesic
const pts = mb.line2points([10.0, 59.0], [10.1, 59.1], 500);

[Copilot]

Pull request overview

This PR implements line2points() in mapbrowser.js, replacing the previous stub with a geodesic-based interpolation that generates evenly spaced points (in meters) between two lon/lat coordinates using OpenLayers sphere utilities.

Changes:

• Implements distance computation via ol.sphere.getDistance(from, to).
• Computes initial bearing and uses ol.sphere.offset() to generate points at fixed meter intervals along the great-circle path.
• Adds basic edge-case handling for invalid/non-positive distance and coincident endpoints.

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