Add a default OAuth client for easier gws setup

[kavin-kr]

New users need to create their own OAuth Desktop app and provide client_secret.json (or env vars) before they can use gws.

Would you consider shipping gws with a default installed app OAuth client ID and client secret, while still allowing users to override with env vars or config?

Ref: gemini-cli - https://github.com/google-gemini/gemini-cli/blob/0957f7d3e2e6080897c56a11547382cc57c33e34/packages/core/src/code_assist/oauth2.ts#L71-L81

Also, if there is another reason why a default client is not used, I would be curious to know it.

[mcorbe]

+1 — Just hit this exact friction with a personal Gmail account.

gws auth setup gets to step 3 (project selected) then fails because the IAP OAuth Admin API (iap.googleapis.com) requires the project to belong to a GCP organization — which personal Gmail accounts don't have.

Even with gcloud fully authenticated, there's no CLI path to create the OAuth consent screen + Desktop client on a personal account. The only option is the Cloud Console UI.

A bundled default client (like gemini-cli does) would remove this barrier entirely for personal users.