[HLSL] Add LinAlg accumulation contention coverage

Add deterministic descriptor-matrix, group-shared-matrix, and descriptor-vector contention across multiple Waves, threads, and dispatch groups. Preserve destination guards, derive repeated totals with checked host arithmetic, execute exact F16/F32 controls on WARP, and retain capability-gated I32 cases for implementations that advertise integer atomic support.

Assisted-by: GitHub Copilot

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 83725f5d-8e98-4c1d-91ee-ad47629e007b

Author: Jack Elliott