Add module READMEs, .gitignore, and remove Bin/ from tracking

Add README.md for each library module documenting API, platform
backends, and usage. Add .gitignore for build artifacts. Remove
pre-built binaries from version control.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

libsst-math/README.md

@@ -0,0 +1,48 @@
+# libsst-math
+
+Type-generic linear algebra library in C, covering vectors, matrices,
+transforms, and geometric queries.
+
+## Vectors
+
+2D, 3D, and 4D vectors in four numeric types each:
+
+- `SST_Vec{2,3,4}{f,d,i,u}` -- float, double, int, unsigned
+
+Operations: add, subtract, multiply, divide, scale, dot, cross, magnitude,
+normalize, project, lerp, weighted sum, negate, abs, reciprocal, sqrt, rotate,
+min/max component, equality. Most have both output and in-place (`Local`)
+variants.
+
+A generic `SST_VectorNf_*` API handles arbitrary-dimension float vectors.
+
+## Matrices
+
+2x2, 3x3, and 4x4 matrices (column-major):
+
+- `SST_Mat{22,33,44}{f,d,i,u}`
+
+Operations: add, subtract, element-wise multiply, scalar multiply,
+matrix-matrix multiply, matrix-vector multiply, transpose, determinant,
+invert, LU decomposition and solve, orthonormality check.
+
+## Transforms (SST_Transform)
+
+4x4 float transform construction:
+
+- Translation, scale, shear
+- Euler rotation (X/Y/Z), quaternion rotation
+- LookAt / LookDir view matrices
+- Perspective and orthographic projection
+- Chained variants (`*C`) for composing onto existing matrices
+
+## Geometry (SST_Geo)
+
+- 2D/3D line segment intersection
+- Point-to-segment closest point and distance
+- Ray-triangle intersection with barycentric coordinates
+
+## Code generation
+
+`VectorN.py` and `MatrixNxN.py` generate the type-specialized `.c` files
+from templates.