Workspace

Reusable scratch for alias-safe matrix operations.

A workspace belongs to one invocation at a time. Independent calls may use distinct workspaces; calls without one own their temporary storage. Buffers never retain an operand and are returned even if arithmetic throws.

Reuse is by exact length, keeping repeated shapes allocation-free without exposing stale tail entries. Retention keeps a bounded number of recently returned lengths, so changing shapes cannot grow the pool indefinitely. Active loans remain valid through nested calls.