chore(vulkan,ci): harden kernel_template binding cap + deliverables-check backslash strip

[lusoris]

Summary

Two small-but-load-bearing hardening fixes uncovered during today's GPU-dedup migration wave. Both are mechanical; they ship together to avoid a one-liner-per-PR ceremony.

• libvmaf/src/vulkan/kernel_template.h: replace the open-coded 8U SSBO-binding upper bound and matching bindings[8] stack array with a named #define VMAF_VULKAN_KERNEL_MAX_SSBO_BINDINGS 16U. Current consumers top out at 10 (the SSIM bundle in ssimulacra2_vulkan.c uses 8); the higher cap absorbs near-future kernels without further edits. Vulkan's conformant minimum for maxDescriptorSetStorageBuffers is 96, so the higher cap remains portable across drivers. No behavioural change — same allowed kernel shapes, same scores, same public C API.
• scripts/ci/deliverables-check.sh: extend the markdown-strip tr -d set to also remove backslashes. PRs created via heredoc-quoted body strings in gh pr create calls escape embedded backticks; the trailing backslash survived the previous strip (which only handled backticks, asterisks, underscores) and broke the - [x].*<item> regex with backslash-space separators between tokens (e.g. AGENTS.md\ invariant note). Bit 18 PRs today.

no docs needed: pure internal hardening — provided_features, scores, and public C API are identical.

Test plan

Fix 2 (deliverables-check.sh): smoke-tested with a heredoc-quoted PR body containing literal-backslash-escaped backticks around AGENTS.md. The script now prints OK (ticked): AGENTS.md invariant note for that line and exits 0 on the full six-deliverable fixture.

PR_BODY="$(cat <<'EOF'
## Test
- [ ] (1) Research digest: \`real-thing\` — no digest needed: trivial CI hardening
- [x] (2) Decision matrix: \`real-thing\`
- [x] (3) \`AGENTS.md\` invariant note: see entry 0001
- [x] (4) Reproducer / smoke-test command: see Test plan
- [x] (5) CHANGELOG fragment: entry under Changed
- [ ] (6) Rebase note: entry 0001 — no rebase impact: fork-local CI/template scaffolding only
EOF
)" BASE_SHA=master HEAD_SHA=HEAD bash scripts/ci/deliverables-check.sh

Fix 1 (kernel_template.h): clean compile + Vulkan smoke + async pending fence tests.

meson setup build-vulkan -Denable_vulkan=enabled -Denable_cuda=false -Denable_sycl=false libvmaf
ninja -C build-vulkan src/libvmaf.so.3.0.0
meson test -C build-vulkan test_vulkan_smoke test_vulkan_async_pending_fence

Result locally: 2/2 OK (test_vulkan_smoke 0.78s, test_vulkan_async_pending_fence 2.27s).

Deep-dive deliverables (per ADR-0108)

• (1) Research digest — no digest needed: trivial fix derived from observation during today's GPU-dedup wave
• (2) Decision matrix — no alternatives: only-one-way fix
• (3) AGENTS.md invariant note — libvmaf/src/vulkan/AGENTS.md updated under "Rebase-sensitive invariants" to document the new VMAF_VULKAN_KERNEL_MAX_SSBO_BINDINGS constant and require both the bound check and the stack-array size to reference it. The deliverables-check fix is too small to need an AGENTS entry; ticked above.
• (4) Reproducer / smoke-test command — see Test plan above.
• (5) CHANGELOG.md fragment — new entry under ### Changed (kernel_template cap as named constant) and under a new ### Fixed section (deliverables-check backslash strip), both in the Unreleased lusoris-fork section.
• (6) Rebase note — no rebase impact: fork-local only — neither file has an upstream counterpart (Netflix/vmaf has no Vulkan backend and no fork-specific CI scripts).

Touched-file lint cleanliness (per CLAUDE.md §12 r12)

pre-commit run --files <touched> passes on all four files (clang-format, shfmt, shellcheck, semgrep, secrets, copyright, conventional-commit hook). One # shellcheck disable=SC1003 annotation added on the tr -d line — tr recognises \\ as a literal backslash escape (the intended behaviour); SC1003 is an informational shell-quoting hint, not a tr-level concern. The disable carries an inline justification per the CLAUDE.md §12 r12 rule.

State.md

No bug closed / opened / ruled-out by this PR; no docs/state.md update needed.

[Copilot]

Pull request overview

This PR hardens two internal maintenance paths in the fork: the Vulkan kernel scaffolding's SSBO-binding limit and the CI script that parses ADR-0108 deliverables from PR bodies. It also updates the Vulkan subtree's rebase notes and the fork changelog to document those changes.

Changes:

• Replace the open-coded Vulkan kernel-template SSBO binding cap and stack-array size with a named constant.
• Extend scripts/ci/deliverables-check.sh to strip backslashes before matching deliverable checklist items in PR bodies.
• Document the Vulkan-side invariant in libvmaf/src/vulkan/AGENTS.md and record the changes in CHANGELOG.md.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
scripts/ci/deliverables-check.sh	Adjusts PR-body normalization so escaped markdown does not break deliverables matching.
libvmaf/src/vulkan/kernel_template.h	Replaces the hard-coded SSBO binding cap with a named constant used by validation and the local bindings array.
libvmaf/src/vulkan/AGENTS.md	Documents the new Vulkan kernel-template invariant for future rebases.
CHANGELOG.md	Adds Unreleased notes describing the kernel-template cap change and deliverables-check fix.

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