Fix geo projections losing their D3 default rotation

[CAOShurong]

Problem

Geo.updateProjection sets projection.rotate([-rotation.lon, -rotation.lat, rotation.roll]) unconditionally. Since projection.rotation defaults to [0, 0, 0], the rotation the d3 projection factory ships with is discarded for the six projections that carry a non-identity default (albers [96, 0, 0], bertin1953, gringorten and peirce quincuncial [-90, -90, 45], sinu mollweide, wiechel) — #7949.

Fix

Capture the factory rotation when the projection wrapper is created (projection.defaultRotation) and compose the user rotation on top of it:

.rotate([
    -rotation.lon + projection.defaultRotation[0],
    -rotation.lat + projection.defaultRotation[1],
    rotation.roll + projection.defaultRotation[2]
])

• projections whose d3 default is the identity (the large majority) produce exactly the same rotation as before in every case;
• at default projection.rotation, the six affected projections now keep their canonical orientation (the reported bug);
• an explicit user rotation now composes relative to the canonical orientation rather than replacing it — for the six projections this changes the meaning of explicit values that were previously compensating for the wiped default; for all other projections explicit behavior is unchanged. The composition semantics are the natural reading of projection.rotation as additional rotation on top of the projection's own orientation, and are what makes both defaults and explicit values consistent without tracking whether each attribute was user-set.

Test

Adds a regression spec asserting albers keeps [96, 0, 0] at defaults, composes (96 - 10) when rotation.lon: 10 is set, and that mercator stays exactly [0, 0, 0].

Fixes #7949