fix(ci): wait for snap gateway readiness

[drew]

Summary

Wait for the Snap-packaged gateway to accept status requests before declaring the Ubuntu Snap canary failed. The service can report active before its listener is ready, which caused an intermittent connection-refused failure.

The same Release Dev commit demonstrated the race: run 33562715502 failed the Ubuntu Snap check while run 33562871938 passed it.

Related Issue

No issue required: this is an obvious localized release-canary reliability fix.

Changes

• Poll openshell status for up to 60 seconds after gateway registration.
• Preserve a hard failure when readiness never arrives.
• Print Snap service state and gateway logs on timeout.

Testing

• mise run pre-commit passes
• Unit tests added/updated (not applicable: workflow-only change)
• E2E tests added/updated (not applicable: canary is the E2E smoke test)

Checklist

• Follows Conventional Commits
• Commits are signed off (DCO)
• Architecture docs updated (not applicable: no architecture change)

[elezar]

@drew could you comment on the difference between this and #2866?

[drew]

I have a scheduled automation that started reviewing flaky tests and opening prs to address findings. This PR is one of those. We can close this and prefer yours.