feat: add GitHub deployment environments for containers, docs, and homebrew

[sbryngelson]

Summary

• Adds environment: blocks to the three workflows that actually deploy artifacts, so they show up in the Deployments sidebar on the repo page
• Splits docs.yml into a build job (runs on all events) and a publish job (runs only on master schedule/dispatch, has the environment) so deployment events only fire on real publishes

Environments added

Environment	Workflow	URL
containers	docker.yml manifests job	https://hub.docker.com/r/mflowcode/mfc
docs	docs.yml publish job	https://mflowcode.github.io/
homebrew	deploy-tap.yml + homebrew-release.yml	https://github.com/MFlowCode/homebrew-mfc

What won't show up (and why)

• Docker Hub images — Docker Hub is external to GitHub; GHCR packages appear under the repo's Packages sidebar automatically once pushed
• Homebrew formula itself — Homebrew is external; the tap link is the closest proxy

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[github-actions]

Claude Code Review

Head SHA: d5030e5

Files changed:

• 4
• .github/workflows/deploy-tap.yml
• .github/workflows/docker.yml
• .github/workflows/docs.yml
• .github/workflows/homebrew-release.yml

Findings

Missing artifact upload in build job (docs.yml)

The docs job was split into build (build + verify) and publish (deploy). The new publish job downloads artifact mfc-docs:

- name: Download Built Documentation Artifact
  uses: actions/download-artifact@v4
  with:
    name: mfc-docs
    path: build/install/docs/mfc

However, the build job has no corresponding actions/upload-artifact step — none was added in this diff, and the original docs job didn't have one (it published directly in the same job). As a result, the publish job will always fail at the download step because the artifact mfc-docs is never produced.

A step like the following is missing from the build job (after the lychee link-check step):

- name: Upload Built Documentation Artifact
  uses: actions/upload-artifact@v4
  with:
    name: mfc-docs
    path: build/install/docs/mfc