fix: Open first workflow file after delayed load

[BenHamiltonGit]

Summary

• Open the first workflow file when the Files tab mounts before files are available and they load afterward.
• Add coverage for the delayed-load case while preserving the existing behavior that closing the last tab keeps all tabs closed.

Why

The new Files tab initializes its selected path/open tab state from the initial files prop. If the overlay mounts while files is empty and the files arrive on a later render, the editor can remain blank until the user manually selects a file. This keeps the initial file-opening behavior working for delayed data without reopening tabs the user intentionally closed.

Testing

• npm run test:run -- WorkflowFilesOverlayLayer.spec.tsx
• npx eslint src/pages/workflowv2/WorkflowFilesOverlayLayer.tsx src/pages/workflowv2/WorkflowFilesOverlayLayer.spec.tsx
• npx prettier --check src/pages/workflowv2/WorkflowFilesOverlayLayer.tsx src/pages/workflowv2/WorkflowFilesOverlayLayer.spec.tsx
• Manually tested locally in the Files tab to verify the default canvas.yaml view still opens normally and tab close behavior is unchanged.

[superplanehq-integration]

👋 Commands for maintainers:

• /sp start - Start an ephemeral machine (takes ~30s)
• /sp stop - Stop a running machine (auto-executed on pr close)

[BenHamiltonGit]

Hope you don’t mind the second PR. After noticing my previous one was superseded by the new Files tab work in #5025, I wanted to do a little extra due diligence against the current main branch.

This one is aimed directly at that new flow: if the Files tab mounts before files are available, it now opens the first file once they load, while preserving the existing tab-close behavior.

I also rebased after #5026 landed and kept the new sidebar-offset coverage intact. I manually tested the Files tab locally as well to verify the default canvas.yaml view still opens normally and tab close behavior is unchanged.

I originally found SuperPlane through a Product Engineer listing and would be glad to connect if future product engineering opportunities open up.

Email: benjamin.joel.hamilton@gmail.com
Portfolio: https://portfolio-2rbk.onrender.com/