feat(frontend): default onboarding to runner mode and make copy prompt mode-aware

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Stack for rivet-dev/rivet

• #5482 feat(frontend): sync compute connect dialog with onboarding …
• #5477 docs: use RIVET_POOL instead of the unread RIVET_RUNNER env …
• #5479 docs: clarify runtime mode guidance across deploy guides
• #5476 feat(frontend): default onboarding to runner mode and make c … 👈
• #5478 refactor(frontend): rename serverfull to serverful
• main

Get stack: forklift get 5476
Push local edits: forklift submit
Merge when ready: forklift merge 5476

_{change pzrzplzk}

[claude]

Review

Reviewed the latest commit (1a5b2ec). Overall this is a clean, well-scoped change: it makes the runner/serverless default provider-aware, trims the copy-agent prompt down to the selected provider doc link instead of a stale multi-link list, and fixes broken /docs/connect/* links to the current /docs/deploy/* paths. Comment quality is good throughout (complete sentences, explains why, matches CLAUDE.md conventions).

Findings

1. Minor UX: the platform switcher can silently discard a prefilled serverless mode (getting-started.tsx:503-525)
SwitchPlatform onClick now always resets mode to defaultRuntimeModeForProvider(option.name). The dropdown options.map renders every provider including the currently-selected one (it gets the checkmark), and its onClick still fires the same reset even when option.name === provider. Since the in-wizard toggle (RunnerConfigToggleGroup) was removed from BackendSetup in this PR, the only way mode can differ from defaultRuntimeModeForProvider(provider) now is the initialRunnerConfig prefill (an existing serverless config detected on load, getting-started.tsx:254-258). If a user has such a prefill and re-opens the switcher to just glance at other options, clicking the already-selected provider resets mode to that provider default and away from the prefilled serverless mode, swapping the deploy screen out from under them. Consider skipping the mode reset when option.name === provider.

2. No test coverage added
getting-started.tsx and agent-prompts.ts have no existing test files, and this PR does not add any. Given the branching logic added here (isServerlessOnlyProvider, defaultRuntimeModeForProvider, the serverless derivation in useAgentInstructionsCode, and the two variants of deploySteps / integrateStep / integrateVerify in agent-prompts.ts), a couple of unit tests around getAgentInstructionsPrompt serverless vs. serverful branching would be cheap insurance against regressions, since this is pure string-building logic with no DOM or network dependency.

3. Verified, not a bug: GCP Cloud Run classified as serverless-only
SERVERLESS_ONLY_PROVIDERS includes gcp-cloud-run alongside the three function platforms. At first glance this looked off since Cloud Run supports long-running containers with --min-instances, but website/src/content/docs/deploy/gcp-cloud-run.mdx documents exactly the serverless paste-your-deployment-URL-into-the-connect-form flow, not a runner/connect-out flow. So this matches the existing docs; flagging it here so a future reader does not have to re-derive it.

4. Two other stale /docs/connect/* links left in the tree (not introduced by this PR, but the same class of bug this PR is fixing)

• frontend/src/components/use-deployment-logs-stream.ts:160 -- rivet.dev/docs/connect/rivet-compute
• frontend/src/content/data.ts:14 -- https://www.rivet.dev/docs/connect/

The website docs tree only has docs/deploy/* now (docs/connect does not exist under website/src/content/docs), so both of these currently point at dead pages. Neither file is touched by this diff, so it is out of scope to fix here, but since this PR is specifically cleaning up this exact URL pattern (agent-prompts.ts changes /docs/connect/rivet-compute to /docs/deploy/rivet-compute), it would be a cheap follow-up to grab these two while the context is fresh.

Other notes (not blocking)

• frontend/src/app/runner-config-toggle-group.tsx: defaultValue="serverful" was changed to match the new default, but since value={mode} is always passed (controlled), Radix ignores defaultValue regardless. Pre-existing dead prop, not introduced by this PR.
• Per CLAUDE.md Frontend Visual Changes guidance, this changes visible onboarding UI (toggle removal, conditional hiding for serverless-only providers). Worth a manual pass in the browser across at least OSS and cloud flavors before merging, since features.compute gates part of this flow.

No security or performance concerns; this is client-side form and copy logic only.