feat(freebyrd): Phase 2 — unified T1+DWT via ScxEngine with per-component domains

decodeAndTransformScx() submits both T1 block decoding and 5/3 DWT
stripe work to ScxEngine in a single engine run. Per-component domains
with ordered sequences ensure T1 (seq 0) completes before DWT stripes
(seq 1+) for each component, while different components interleave
naturally across the worker pool.

9/7 DWT falls back to TaskFlow after engine run (requires file-local
utility functions not accessible from the scheduler file).

Author: Grok Compression