Open a $20 credit checkout from beam setup and drop semicolons from CLI copy

[luke-lombardi]

At the credits step, beam setup now shows one sentence ("This workspace has no credits yet."), and pressing Enter opens a $20 Stripe Checkout for the signed-in account through internal-api's new POST /v2/oauth/cli/checkout (beam-cloud/internal-api#321). If that endpoint isn't available, it opens the dashboard credits page as before. The header no longer shows the workspace ID, and success reads "Added credits". The sentence is derived from the gateway's message, so the new wording shows against both the current and the updated internal-api messages.

CLI, onboarding and login messages no longer use semicolons. Bumps the SDK to 0.1.280.

Validation: 601 SDK tests passed, 2 skipped. New onboarding cases cover the checkout request and the URL it opens, the fallback to the credits page, and the one-sentence reason for old and new server messages. Ruff passed on the changed files.

Made with Cursor

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Summary by cubic

Pressing Enter at the credits step in beam setup now opens a $20 Stripe Checkout for the signed-in account, falling back to the dashboard credits page if checkout is unavailable.

• Shows the credit reason as a single sentence without the dashboard link or workspace ID; success now reads "Added credits".
• Removes semicolons from CLI, onboarding, and login messages and bumps and locks the SDK to 0.1.280.

^{Written for commit 9df60de. Summary will update on new commits.}

[jackf-beamcloud]

Looks good: Enter at the credits step POSTs {total_cents_amount: 2000} to <auth_url>/cli/checkout with the context's own token (matches internal-api#321), only opens https URLs from a 201, and falls back to the dashboard link otherwise. The rest is copy and the 0.1.280 bump. Non-blocking: if the gateway's first sentence is the one carrying the link (e.g. "Add credits at https://..."), credit_reason will still print the URL, and if neither checkout nor a link is available the user only sees the error after pressing Enter.