chore(deps): upgrade pydantic-ai-slim to 2.34 and re-sync vendored data-stream types (#15714)

* chore(deps): upgrade pydantic-ai-slim to 2.34 and re-sync vendored data-stream types

pydantic-ai 2.34.0 added an `id` field to `ReasoningUIPart` so the Vercel
AI adapter no longer rejects reasoning parts carrying a client UI part ID.
Add the same field to the vendored copy, point the vendored headers at
v2.34.0, raise the floor to >=2.34.0, and drop the <2.34 unit-test cap.

2.35.x carries identical vercel_ai sources but is still inside the 3-day
exclude-newer quarantine, so the lock resolves to 2.34.0 for now.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017TyTrmUmSxJirG1vjijmFJ

* chore: regenerate OpenAPI schema and clients for ReasoningUIPart.id

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017TyTrmUmSxJirG1vjijmFJ

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Co-authored-by: Claude Fable 5 <noreply@anthropic.com>