fix(ci): skip Node build when CLI is unaffected

[opencode-agent]

Summary

• check whether @opencode-ai/cli or its dependency graph is affected before verifying the Node build
• skip both Node 26 setup and the Node build/service smoke when unrelated packages change
• keep manual workflow runs unconditional and preserve the existing behavior after earlier step failures

Verification

• bun x prettier --check .github/workflows/test.yml
• verified unchanged revisions select zero affected CLI packages
• verified CLI and dependency changes select the CLI package

Requested by: @Brendonovich (Brendan via Slack)