Add matrix.transform-rotate-aer (azimuth/elevation/roll) helper

[RaulDurand]

This PR adds a convenience rotation constructor to matrix:

transform-rotate-aer(azimuth, elevation, roll: 0deg)

Behavior

• Builds a 4x4 rotation matrix from azimuth/elevation with optional roll.
• Uses the viewing convention:
  • z points up
  • x points toward the viewer
  • aligned with the common azimuth/elevation camera interpretation used by plotting tools (including matplotlib).
• Optional roll around the current viewing axis after azimuth/elevation.

Implementation

• Added internal helper:
  • _rotate-axis-angle(ax, ay, az, angle) (axis-angle rotation matrix using the Rodrigues' formula)
• Added public function:
  • transform-rotate-aer(azimuth, elevation, roll: 0deg)

[johannes-wolf]

Nitpick, otherwise fine.