Follow-up to #1132, which types the integration suite's createClientFn as a union of the v1 (@modelcontextprotocol/sdk) and v2 (@modelcontextprotocol/client) clients.

Once the v2 SDK leaves beta, migrate all suite transports to the v2 client — it negotiates both protocol eras via connect(..., { mode: 'auto' }) — and remove:

• the union type from createClientFn,
• the v1-client narrows in the legacy-only Tasks cases,
• the v1 client from the suite entirely.

Blocked on: v2 SDK stable release.