feat(onboarding): guide users through their first app

[Shreyasshukla957]

Summary

• guide a new organization through selecting its first app, connecting an MCP client, and trying four practical agent prompts
• preserve the normal integration browser and add-integration behavior outside onboarding
• store per-organization prompt progress locally and cover it with focused tests
• update existing cloud onboarding flows for the new first-app step

This is a client-side guided flow. It does not claim to verify a live MCP connection because the current main branch has no server-backed setup-progress API.

Validation

• bun run lint
• bun run typecheck (45/45 tasks)
• bun run --cwd packages/react build
• bun run --cwd apps/cloud test -- onboarding-progress.test.ts (2 passing)
• bun run --cwd packages/react test -- analytics.test.ts (6 passing)
• bunx oxfmt --check on changed files
• git diff --check

Environment limitations

• The full cloud suite has one unrelated Windows path-separator failure: 831/832 tests pass.
• The full workspace suite stops on desktop POSIX permission assertions that Windows cannot satisfy.
• Cloud browser E2E and the production cloud build cannot start on this machine because their bootstrap depends on POSIX lsof and the Vite loader rejects a TypeScript config import on Windows.
• Repository-wide format and route checks report unrelated CRLF-only generated-file differences.