chore: Standardize cf workbench integration

[eersnington]

Reorganizing a lot of things within the workbench mainly to reduce slop code and maintaining a single source of truth.

• Standardized both benches on GET/POST /api/workflows/:key
• Vite now owns complete Sideffect behavior coverage workflows.e2e.test.ts
• TanStack covers framework delegation, API exposure, and native workflow coexistence: integration.e2e.test.ts
• Discovery/build coverage is separated in each bench
• Shared only mechanical server/polling code in workflow-http.ts
• Renamed shared case metadata to workflow-cases.ts
• Native workflow implementations remain explicit in both hosts intentionally (due to the requirement of bindings being unique in a Cloudflare Account)

Validation:

• bun run check --fix — passed
• bun run test — 67 tests passed
• Vite E2E — 17 tests passed
• TanStack E2E — 10 tests passed
• Both builds and Wrangler dry-runs passed