ci(docker): skip PR triggers — build only on push to main + release

[parth0025]

Summary

Stop running the Docker multi-arch build on PRs. From now on, it only runs when something actually needs to be published:

• release: published → publishes versioned tags + latest (release-please-driven)
• push: branches: [main] → publishes edge + main-<sha>
• workflow_dispatch → manual run from the Actions UI

The pull_request trigger is removed.

Why

Multi-arch docker builds (amd64 + arm64 via QEMU emulation) are slow:

Scenario	Build time
First-time / cold cache	12–18 min
Warm GHA cache, only source changed	3–6 min
Warm GHA cache, Dockerfile changed	8–12 min

Even the cached case is longer than every other CI check in this repo. On PR #216 today, the build was visibly blocking review for ~15 minutes per attempt. Since PR builds are push: false anyway (verification-only, nothing pushed to a registry), the value-to-cost ratio is poor.

Trade-off

Before	After
Docker breakage caught at PR-review time	Docker breakage caught at post-merge time on main
15 min added to every Docker-touching PR	PRs are fast again
push: false build artifact discarded	(same — PR builds were never published anyway)

If a Docker-breaking change does land on main:

• release.yml will fail when release-please tries to build for the release tag — surfaced before users see anything
• Revert via "Revert" button on the offending PR → 30 seconds

What still triggers a build

Event	Triggers?
PR opened against main (touches Docker files)	❌ No (changed)
PR opened against main (no Docker changes)	❌ No (was already no)
PR opened against staging	❌ No (was already no — we removed staging earlier)
Push to main (e.g., PR merged)	✅ Yes — builds + pushes edge + main-<sha>
Push to staging	❌ No (was already no)
Release tag published (release-please)	✅ Yes — builds + pushes vX.Y.Z, latest, X.Y, X
Manual trigger from Actions UI	✅ Yes

Files changed (1)

File	Change
.github/workflows/docker.yml	Remove pull_request trigger + its paths filter; add inline comments documenting each remaining trigger

Diff: +5 / -10 lines.

Test plan

• After merge, open any PR touching Dockerfile → Docker workflow should NOT run on it
• After merge, push a commit to main (or merge a PR to main) → Docker workflow SHOULD run and push edge + main-<sha> to GHCR
• Trigger workflow_dispatch manually → should run on demand
• When release-please publishes the next release, the release: published event should fire the workflow + push versioned tags

Compatibility

✅ No conflict with any open PR (touches only .github/workflows/docker.yml)
✅ Doesn't touch the Dockerfile, docker-compose.yml, or any build artifact
✅ Doesn't change what gets published — only when it gets built

🤖 Generated with Claude Code

[coderabbitai]

Important

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch ci/docker-skip-pr-trigger

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