v0.8.3

Added

• Support unit-aware out for sum, mean, median, std, var, cumsum,
  concatenate, stack, and add.reduce/accumulate. Require the exact result shape,
  preserve target identity, unit, and dtype, and stage computation, conversion,
  and casting before writing. Argmin/argmax accept bare integer ndarray outputs.
• Document function/reduction output casting and add regressions for scaled
  units, positional outputs, overlapping/strided buffers, and unchanged outputs
  on failure, plus installed-consumer type checks.