Add Mat44 perspective and orthographic projections

[crertel]

Adds Mat44.perspective/4 and Mat44.ortho/6 for projecting right-handed camera coordinates looking down -Z. Both use row vectors and map the near and far planes to normalized device depths -1 and +1, matching the OpenGL projection convention.

perspective(fov_y, aspect, near, far) takes a vertical field of view in radians and width/height aspect ratio. It requires 0 < fov_y < pi, positive aspect, and 0 < near < far; invalid parameters raise ArithmeticError. Its depth coefficients avoid multiplying near and far together, preventing avoidable overflow or underflow.

ortho(x_min, x_max, y_min, y_max, near, far) supports asymmetric volumes, reversed bounds for axis flips, and zero or negative near/far distances. Each pair must have nonzero extent; equal endpoints raise ArithmeticError.

The docs and examples show that perspective projection requires apply_left/2 followed by division by the output w; transform_point/2 discards that coordinate. Orthographic projection preserves w and supports transform_point/2 directly. Float typespecs and explicit float clauses with numeric fallbacks are preserved.

Validation: 570 tests and 5 doctests pass with 100% line coverage. Tests cover all near/far corners, known matrices, foreshortening and depth, homogeneous coordinates, camera translation composition, inverse round trips, reversed and fractional bounds, integer/mixed inputs, large/small distances, and invalid parameters. Formatting, compilation with warnings as errors, and documentation generation pass.

Part of #44. This PR is based on master and is independent of the camera/billboard implementation in #66.

[coveralls]

coverage: 100.0%. remained the same — 44-mat44-projection into master

[coveralls]

coverage: 100.0%. remained the same — 44-mat44-projection into master