Introduce ProjectionKind and capability-based projection dispatch

[trasch]

Summary

Phase 1 of making the projection system generic ( groundwork for supporting a wider range of CRSs beyond the fixed set of EPSG:4326, EPSG:3857, EPSG:4978 and noSRID).

Instead of switching on specific EPSG codes, algorithms now dispatch on a semantic projection category. New projections registered in a later phase will automatically get sensible default behavior.

New API

• ProjectionKind enum: .geographic / .planar / .geocentric / .undefined (new file ProjectionKind.swift)
• Projection.kind, plus convenience flags isGeographic, isPlanar, isGeocentric, hasSRID
• Projection.wraparoundExtent: Double? — the horizontal wraparound boundary (±180° for EPSG:4326, ±originShift for EPSG:3857, nil for EPSG:4978/noSRID)
• Projection.crsLength(fromMeters:) — shared meters-to-CRS-units conversion (replaces several duplicated tolerance / 111_325.0 switches)

Refactored to kind/capability dispatch (behavior-neutral)

• Geodesic ops (distance, bearing, destination, midpoint, rhumb bearing/distance/destination): dispatch on ProjectionKind; geographic/planar/geocentric compute via the EPSG:4326 pivot, noSRID keeps its planar fallback
• AntimeridianCutting: the duplicated EPSG:4326/EPSG:3857 helper implementations (~150 lines) collapsed into single implementations parameterized by wraparoundExtent; crossesAntimeridian / cutAtAntimeridian dispatch on wraparoundExtent
• BoundingBox: date-line splits in contains / intersects / intersection, padding, expansion, size and normalized() now dispatch on kind / wraparoundExtent
• ~20 algorithm files: antimeridian-span checks (projection == .epsg4326 → isGeographic), unit-conversion switches → crsLength(fromMeters:), grid cell sizing → !isGeographic, geocentric-recurse checks → isGeocentric

Intentionally unchanged

Per-CRS switch matrices in Coordinate3D.projected(to:), clamped(), BoundingBox.expanded(byDistance:), Random.worldBox, the WKT/WKB coders and MapTile remain as-is — they become registry data in phase 2.

Also included

• .swiftformat configuration file for the project's formatting conventions

Testing

• New tests in ProjectionTests.swift cover kind, the kind flags, wraparoundExtent and crsLength(fromMeters:)
• Full suite passes: 2424 tests in 172 suites, no behavior changes

[trasch]

Superseded by #250, which consolidates the full projection-genericity chain into a single reviewable PR. All commits are unchanged in #250.