Add musllinux wheel packaging for Alpine

[jtwigg-luma]

Why

Upstream contentauth/c2pa-python only publishes manylinux (glibc) wheels. Alpine (musl) cannot load those wheels; the sdist pulls gnu natives that fail at dlopen; compiling Rust inside every image build is too slow.

This fork ships musllinux wheels so Alpine can import c2pa without a per-image Rust compile. The Python API is unchanged. macOS and glibc Linux keep using PyPI.

Divergence is kept small: one build script, one workflow, MUSLLINUX.md, and disabled unused Adobe Actions so musl tags do not fan out into their Build/PyPI/Pages/Jira matrix.

What

• scripts/build_musllinux_wheel.sh — build musllinux_1_2_x86_64 in python:3.14-alpine
• .github/workflows/build-musllinux-wheel.yml — CI + GitHub Release on v*-musl* tags
• MUSLLINUX.md — why this fork exists + how to upgrade
• Disable unused upstream Actions (stub workflow_dispatch only)

Consume

dependencies = [
  "c2pa-python==0.37.1",
]

[tool.uv]
find-links = [
  "https://github.com/<org>/<repo>/releases/expanded_assets/v0.37.1-musl.1",
]

Do not pin a direct musllinux wheel URL (forces one platform everywhere).

Test plan

• Wheel installs in python:3.14-alpine → import c2pa + Context() OK
• Release v0.37.1-musl.1 published with wheel asset
• CI musllinux workflow succeeds on workflow_dispatch
• Approve + squash-merge (org ruleset requires 1 review)

[jtwigg-luma]

Ready to squash-merge. Org ruleset Company wide SDLC/SOC-2 requires 1 approving review (current_user_can_bypass: never), so the author cannot merge.

Please approve, then squash-merge (single commit on main).

Contents:

• scripts/build_musllinux_wheel.sh + build-musllinux-wheel.yml
• LUMA.md (why / how to upgrade)
• Upstream Adobe Actions disabled (stub workflow_dispatch only)

[cursor]

PR Summary

Low Risk
Changes are limited to CI, a Docker build script, and docs; no runtime Python API or auth/data-path changes.

Overview
Adds musllinux wheel build and release for Alpine/musl, where upstream only ships manylinux wheels.

scripts/build_musllinux_wheel.sh runs a Docker build on python:3.14-alpine: clones the pinned c2pa-rs tag, compiles c2pa-c-ffi, stages the .so under the existing gnu artifact layout, and runs bdist_wheel with --plat-name musllinux_1_2_x86_64, including a smoke import c2pa check. .github/workflows/build-musllinux-wheel.yml runs that script on workflow_dispatch or v*-musl* tags, uploads the artifact, and attaches wheels to a GitHub Release on tag push.

Upstream Adobe workflows (build.yml, PyPI/docs/memray, Jira issue label sync) are stubbed to workflow_dispatch only so musl tags do not trigger multi-platform builds or PyPI publish. MUSLLINUX.md documents fork rationale, upgrade steps, and uv find-links consumption; README.md points Alpine users there.

^{Reviewed by Cursor Bugbot for commit 93d1b24. Bugbot is set up for automated code reviews on this repo. Configure here.}

[jtwigg-luma]

Superseded by a PR from branch musllinux-wheels (no Luma branding in branch/diff).