Prepare JPEG 2000 Part 1/T.803 0.8.1 release

[jcwal1516]

Summary

• add the unpublished j2k-t803 framework and fail-closed official-corpus workflow for ISO/IEC 15444-4:2024 / ITU-T T.803 v3
• establish the CPU decoder evidence for Profile-1 Cclass-1, Profile-1 Cclass-1HF, and Annex G JP2 reader behavior
• add truthful CUDA and Metal adapter-IUT evidence with per-stage CPU/device/hybrid reporting
• publish deterministic Annex D/F encoder ICS matrices validated through the pinned T.804 OpenJPEG decoder as informative encoder evidence
• add fixed, benchmark-backed Auto routing and repair exact Metal irreversible-encode parity
• prepare the workspace as version 0.8.1 without using a generic “fully Part 1 compliant” claim

Evidence

Exact candidate SHA: a75c4f190e9e0dcfc85a783e3d1646de4d5dd30b

• CPU T.803: 90/90 with zero skips on Linux x64, macOS arm64, and Windows x64
• CUDA adapter-IUT: 90/90; 0 device-native, 48 hybrid, 42 CPU-routed
• Metal adapter-IUT: 90/90; 0 device-native, 48 hybrid, 42 CPU-routed
• encoder matrix: CPU 28/28, CUDA 25/25, Metal 25/25 through the T.804 OpenJPEG reference decoder
• p0_13: production output independently matches OpenJPEG component-for-component across all 257 components before harness normalization
• Auto routing: all compared outputs are identical; CUDA promotes 18/36 measured decode cells and Metal promotes 4/36 measured cells under the ≥10% and non-overlapping 95% CI rule

Validation

• cargo xtask ci
• cargo xtask release-cpu
• full CUDA release validation on an NVIDIA RTX 4070 SUPER
• cargo xtask release-metal --mode full on an Apple M4 Pro
• cargo xtask stable-api
• cargo xtask semver
• cargo xtask package
• cargo xtask release-integrity --publish
• coordinated exact-SHA cargo xtask t803 verify --scope all
• exact-SHA CUDA and Metal Auto-routing benchmarks and artifact verification

The tag and package publication remain blocked until this exact SHA reaches origin/main, the hosted full and GPU validation artifacts complete, and cargo xtask release-status --sha a75c4f190e9e0dcfc85a783e3d1646de4d5dd30b --scope all passes.