Implement simple vector and tensor types

[Jullija]

Added

Types

• cartesian_vector<T> — fixed 3D vector
• cartesian_tensor<T,R,C> — matrix/tensor with R,C ∈ [1..3]

Vector ops (a,b : cartesian_vector ; s : scalar)

• a + b — elementwise addition
• a - b — elementwise subtraction
• a % b — elementwise modulo (% for integral, fmod for floating)
• a * s, s * a — scalar multiply
• a / s — scalar divide
• a ⋅ b (scalar_product, alias dot) — dot product → scalar
• a × b (vector_product, alias cross) — cross product → vector
• |a| (magnitude, norm) — Euclidean length (floating reps only)
• a/|a| (unit) — unit vector (floating reps only)

Tensor ops (A,B : cartesian_tensor<R,C> ; M:N, matching dims; s: scalar)

• A + B, A - B — elementwise
• A % B — elementwise modulo (% / fmod as above)
• A * s, s * A, A / s — scalar scale
• A · x (matvec) — 3×3 tensor–vector product → vector
• A · B (matmul) — matrix multiply (R×K)*(K×C) → (R×C)
• A : B (double_contraction) — scalar (sum of elementwise products)
• a ⊗ b (outer_numeric) — vector outer product → 3×3 tensor

[Jullija]

Hi! Thank you so much! I'll start reading and implementing changes - thank you and sorry in advance for any problems! :)

[Jullija]

@mpusz could you help me fix the pipeline? I tried in some many ways and I have no idea how to fix it :c

[mpusz]

I am currently on vacation in Hawaii, so I don't have much time to look into it. I will check it out when I am back.