Go ui_api: add `PUT /v1/environments/:env/ds/nodes/:id` and `DELETE /v1/environments/:env/ds/nodes/:id`

[sud0n1m]

As of 2026-05-14, the Go ui_api now supports POST /v1/environments/:env/ds/nodes for design-studio node creation (huge unlock — thank you). But for per-node updates and deletes, agents still have to fall back to:

• PATCH /design-studio/api/workspaces/:ws/nodes/:id on the legacy Design Studio surface for updates, or
• POST /v1/environments/:env/ds/node_actions/bulk_delete with a single-element node_ids array for deletes.

Both work (the legacy surface now accepts service-account JWTs, which it didn't before), but the surface split is awkward — the create returns from the Go ui_api, then you switch hosts/paths to mutate the same resource.

Suggested

Add PUT /v1/environments/:env/ds/nodes/:id (or PATCH) and DELETE /v1/environments/:env/ds/nodes/:id to the Go ui_api so a node's full CRUD lives on one surface.

Why it matters

Today's split makes the cio agent skill more confusing (the ds resource only shows create on its schema; agents have to learn the legacy path separately). Consolidating would let cio schema ds describe the full lifecycle.