ci: publish docker image on release

[jasonp2323]

What type of PR is this?

• Bug fix
• New feature
• Documentation
• Refactoring
• CI/Build

Description

Adds multi-architecture Docker image publishing to the release workflow and
documents container usage in the README. Also fixes a stale Go version pin
that has broken the release workflow since the go 1.25 bump.

CI (.github/workflows/release.yml):

• Added docker/setup-qemu-action@v3 and docker/setup-buildx-action@v3 steps to the existing docker job
• Added platforms: linux/amd64,linux/arm64 to the docker/build-push-action step, so releases now publish multi-arch images to ghcr.io/pmady/gpu-mcp-server (arm64 covers Grace Hopper / GH200 GPU servers)
• Images remain tagged with both the release version (e.g. v0.1.0) and latest
• Fixed the release job's setup-go step, which pinned go-version: "1.23" while go.mod requires go >= 1.25 — with GOTOOLCHAIN=local this fails the test step, so any release tag pushed today would fail before building anything. Now uses go-version-file: go.mod so it can't drift again. (Found by rehearsing the release on my fork.)

Docs (README.md):

• New "Docker" section with docker pull / docker run examples, the NVIDIA Container Toolkit requirement for --gpus all, a note that -i is required since the server speaks MCP over stdio, and an MCP client config snippet that launches the server via docker run

Testing — full release rehearsal on my fork:

• Pushed a test tag; the release workflow ran end-to-end (binary release + docker job) and published to my fork's GHCR
• Verified via docker buildx imagetools inspect that the manifest list contains both linux/amd64 and linux/arm64
• Verified both image variants boot: --version on the amd64 image natively and on the arm64 image under QEMU emulation
• Not yet exercised: NVML initialization on physical GPUs (--gpus all). I'm following up with a proposal for reusable GPU test infrastructure that will validate released images on real T4 (amd64) and T4G (arm64) hardware.
• Pushed a test tag; the release workflow ran end-to-end (binary release + docker job)
  and published to my fork's GHCR:
  successful run
  published package

Related Issue

Fixes #27

Checklist

• Tests added/updated (CI/docs change — no testable Go surface)
• Documentation updated (if applicable)
• make test passes
• make lint passes
• Commits are signed off (git commit -s)

AI Assistance Disclosure

Per AI_GUIDELINES.md: the release.yml was modified with the help of AI
(Claude Code). I reviewed the changes, performed make and lint tests
and validated the release workflow by merging and tagging onto my own fork.
Commits are DCO signed-off.

Contributor Info

• Name: Jason Paquette
• Location: Boston, MA
• Company / Affiliation: