fix(cursor-depth): hybrid keeps the line of sight — release 1.37.1

[dfattal]

In 1.37.0's hybrid anchor, when the depth under a still pointer changed, the sprite rose along the display normal. For an off-axis viewer that pulls it off the click point (27 px in the runtime's off-axis capture). It now keeps the line of sight from the last pointer move and sits on that line at the current depth:

• a head move leaves it fixed, so it parallaxes;
• a depth change slides it along the line, so it stays on the click point;
• it is continuous at the moment the pointer stops.

This is the same rule the runtime adopts (DisplayXR/displayxr-runtime#1847).

Evidence:

• npm test: 849 pass. Two new tests: an off-axis depth change, where the sprite stays exactly on the click point while world mode drifts more than 5 mm, and a head moving nearer, where the sprite keeps the depth the content needs.
• Three deliberately broken versions are all caught: dropping the distance ratio, using the current eye instead of the anchor-time eye, and a bad stored distance.
• test:e2e:cursor: 6/6 pass (both engines, model and splat; screen still slides, hybrid and world stay fixed).

Bumps to 1.37.1. After merge, tag sdk-v1.37.1.

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