mutable/vector Design

Responsibilities

• Provide an execution-oriented Vector[T] backed by Array[T].
• Support direct indexed reads and writes for workloads that need in-place updates.
• Keep non-inplace algebraic helpers available for value-producing transforms.
• Keep scalar-reducing and aggregate helpers such as dot() in the mutable package.

Invariants

• *_inplace methods mutate the existing vector and return Unit.
• map, scale helpers, zip_with, and matrix conversion helpers return new values.
• Vector algebra should stay aligned with @immut.Vector for the shared operation subset.
• Length-sensitive helpers such as dot() and lin_comb(...) reject inconsistent inputs explicitly.