feat(workflows): unify workflow and actor API

[NathanFlurry]

Summary

• re-export RivetKit from @rivet-dev/workflows while keeping RivetKit as a peer dependency scoped to >=2.3.11 <2.4.0
• support workflow({ state, run, actions }) while preserving the workflow runtime and actor capabilities
• make workflow definitions compose through setup, including mixed workflow/actor registries and actor routing
• target the current RivetKit workflow-host API from test(rivetkit): add versioned workflow upgrade fixtures actors#5578
• update package verification, docs, fixtures, persistence, Inspector integration, and runtime coverage for the unified API

Dependency

Requires rivetkit@2.3.11, containing rivet-dev/actors#5578.

Testing

• pnpm check-types
• pnpm test (246 tests)
• pnpm test:e2e
• pnpm format:check
• pnpm check:boundaries
• pnpm build
• pnpm verify:pack