Infrastructure: Publish Docker dev image and document container CI workflow

[PurHur]

Problem

Makefile references ircmaxell/php-compiler:16.04-dev / 18.04-dev, but images are not published to Docker Hub (docker pull 404). Runforge/harness hosts must not apt-install LLVM/PHP; they need a reproducible container workflow.

#73 tracks Ubuntu 22.04 + PHP 8.2 upgrade; this issue is publish + docs for any supported image.

Goal

One documented command runs full CI inside Docker with repo mounted:

docker run --rm -v "$(pwd):/compiler" -w /compiler <image> ./script/ci-local.sh

Tasks

• Add Docker/dev/ubuntu-22.04/ (or refresh Infrastructure: Upgrade Docker images to Ubuntu 22.04 + PHP 8.2 toolchain #73) with PHP 8.2 + extensions from README
• GitHub Actions job: build image, push to ghcr.io/PurHur/php-compiler:dev
• Makefile target test-docker wrapping the above
• README section: "Container development (required on harness hosts)"
• Bundle LLVM 9 install inside image OR mount .llvm volume
• Do not modify Runforge harness docker-compose.yml

Acceptance criteria

Fresh clone on a host with only Docker:

docker pull ghcr.io/PurHur/php-compiler:dev
make test-docker   # or documented docker run

→ PHPUnit completes (VM tests at minimum).

Dependencies

• DevEx: Document and stabilize host-based workflow (ci-local.sh, LLVM 9) #46 host workflow (reference)
• Infrastructure: Upgrade Docker images to Ubuntu 22.04 + PHP 8.2 toolchain #73 22.04 toolchain
• Infrastructure: LLVM 9 → 14+ upgrade and CI matrix #174 LLVM path

Files

• Docker/, Makefile, README.md, .github/workflows/

[PurHur]

Progress in #228:

• Added Docker/dev/ubuntu-22.04/ (PHP 8.2 via ondrej PPA + LLVM 14 dev packages)
• make docker-build-22, make test-docker, script/docker-ci-local.sh (tar fallback when bind-mount is empty)
• README "Container development" section

Remaining: publish image to ghcr.io (requires registry push in maintainer environment); optional GHA publish job is out of scope for harness-only CI.

[PurHur]

Linked work (backlog architect)

#73 — 22.04 Dockerfile + make test-docker landed; remaining: publish image + deprecate 16.04 default make test.

#237 ✅ — LLVM 9 baked at /opt/llvm9 in dev image; unblocks #98 in Docker.

#245 — Document host vs Docker vs GHA skip matrix (reduces confusion with #98 / #234).

Publish acceptance unchanged; verification remains local/Docker only — no workflow edits required to close.

[PurHur]

De-duplication (backlog architect — batch 8)

Already on master (narrow remaining scope)

• ✅ Docker/dev/ubuntu-22.04/Dockerfile, make docker-build-22, make test-docker
• ✅ README container section
• ✅ LLVM 9 at /opt/llvm9 (Infrastructure: Pre-install LLVM 9 in 22.04 dev Docker image for JIT/AOT CI #237 closed)

Split with sibling issues

Issue	Owns
#73	FFIMe/legacy 16.04 deprecation, closing when 22.04 path is primary
#249	make test → test-docker default
#245	CI matrix docs (host / Docker / GHA skips)
#98 / #250	JIT compliance execution + guard
#234	Serve tests on by default in Docker

Still open here

• docker pull ghcr.io/PurHur/php-compiler:dev (or documented PHP_COMPILER_DEV_IMAGE)
• GHA optional job to build/push image — not required for harness; local make docker-build-22 suffices

Harness verification (no GHA):

make docker-build-22
make test-docker