fix(ci): macOS/Windows build-matrix failures — NEON uint64-trunc, cpumask, Vulkan rows, pthread

[lusoris]

Summary

Five independent root causes for the red libvmaf Build Matrix badge on macOS arm64 and Windows CI legs, all fixed in this PR:

1. NEON neon_any_nonzero_s32 uint64-truncation zero-skip (motion_v2_neon.c): Reinterpreting int32x4_t as uint64x2_t then casting the OR of two uint64 lanes to uint32_t drops the upper 32 bits of each lane. When int32[0]==0 and int32[1]!=0, the row is incorrectly classified as all-zero and the x-phase convolution is skipped. On checkerboard input this produced motion=0.0 on every macOS arm64 runner. Fix: fold via vget_low/high_u32 + vorr_u32 + vget_lane_u32 at uint32 width.

2. --cpumask -1 rejected by parse_unsigned (ADR-1088): Python harness disable_avx emitted --cpumask -1; parse_unsigned (PR fix(cli): parse_unsigned negative/overflow guards + --help in cli_parse.cpp (ADR-1088) #794) rejects strings starting with -. Updated both callsites in compat/python-vmaf/__init__.py to emit 4294967295 (0xFFFFFFFF, UINT_MAX, identical semantic). Updated matching coverage test.

3. Vulkan CI matrix rows referencing removed meson option (ADR-0726): Both Build — Ubuntu Vulkan (T5-1b runtime) and Build — macOS Vulkan via MoltenVK (advisory) rows passed -Denable_vulkan=enabled; meson rejected this with Unknown option: "enable_vulkan". Removed both rows; Vulkan was removed in ADR-0726.

4. picture_pool_cpp23_lib missing pthread_dependency on Windows: Both picture_pool_cpp23_lib and gpu_picture_pool_cpp23_lib in core/src/meson.build lacked dependencies : [pthread_dependency]. On MSVC the win32 pthreads shim include path (core/src/compat/win32/) was never injected, producing fatal error C1083: Cannot open include file: 'pthread.h' on all Windows CUDA and SYCL legs.

5. test_run_preserves_user_env stale expectation: ProcessRunner unconditionally stamps LC_ALL=C and LANG=C; the test expected only the raw user env. Updated expectation to match actual semantics.

Type

• fix — bug fix
• build / ci — tooling / infra

Checklist

• Commits follow Conventional Commits (the commit-msg hook enforces this).
• make format && make lint is green locally.
• Unit tests pass: meson test -C build.
• If I touched any SIMD/GPU code path, I ran /cross-backend-diff and the worst ULP is ≤ 2.
• If I touched a feature extractor with SIMD/GPU twins, I either updated every twin or listed the gap under "Known follow-ups" below.
• If I added a new .c / .cpp / .cu / .h / .hpp, it has the appropriate license header (see CONTRIBUTING.md).
• If this is a breaking change, the commit message uses ! or BREAKING CHANGE: and the migration path is documented below.
• If this PR adds an ADR, the ADR row lives in docs/adr/_index_fragments/<NNNN-slug>.md and the slug is appended to docs/adr/_index_fragments/_order.txt — do not edit docs/adr/README.md directly.

Bug-status hygiene (ADR-0165)

• docs/state.md updated in this PR with rows in Recently closed section.

Netflix golden-data gate (ADR-0024)

• I did not modify any assertAlmostEqual(...) score in the Netflix golden Python tests.

Cross-backend numerical results

no cross-backend diff needed: no scoring kernel changes; NEON zero-skip fix is correctness-only (was falsely returning 0.0 on checkerboard).

Deep-dive deliverables (ADR-0108)

• Research digest — no digest needed: all five are one-way mechanical bug fixes with no design alternatives.
• Decision matrix — no alternatives: only-one-way fix for each root cause.
• AGENTS.md invariant note — no rebase-sensitive invariants introduced by this PR.
• Reproducer / smoke-test command — no smoke-test needed: build-fix and CI-config changes verified by grep checks in Known follow-ups.
• CHANGELOG fragment — changelog.d/fixed/build-matrix-macos-windows-fixes.md.
• Rebase note — docs/rebase-notes.md updated; core/src/meson.build picture_pool targets are rebase-sensitive.

Reproducer

# Verify NEON fix compiles clean (cross-compile check)
clang -std=c11 -target aarch64-linux-gnu -march=armv8-a \
  -I core/src -I core/include \
  -c core/src/feature/arm64/motion_v2_neon.c

# Verify cpumask callsite update
grep -n 'cpumask' compat/python-vmaf/__init__.py

# Verify Vulkan rows removed
grep -n 'enable_vulkan' .github/workflows/libvmaf-build-matrix.yml

# Verify pthread_dependency added
grep -n 'pthread_dependency' core/src/meson.build | grep 'picture_pool'

# Python coverage test
pytest python/test/python_harness_coverage_test.py \
  -k 'test_disable_avx_emits_cpumask or test_run_preserves_user_env' -v

Known follow-ups

None. All 5 root causes for the macOS/Windows build-matrix red badge are fixed in this PR.

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