Research: Studio PI harness replacement seam

[chubes4]

Identify the smallest Studio integration seam for this runtime substrate.

Goal

Find one Studio path that could consume the runtime contract instead of coupling directly to the PI harness.

Scope

• Locate current PI harness call sites.
• Identify the minimal create/execute/artifact flow Studio needs.
• Keep this as research only until Hello Runtime works.

Acceptance Criteria

• Notes document the smallest viable Studio swap-in spike.
• No Studio code changes in this repo.

[chubes4]

Triage: keep open, but this is not the fastest route to a real test. Studio integration should follow after one control-plane consumer proves create/execute/artifact flow. The smallest likely seam remains the Playground server/PI harness boundary, but it is a product/UI spike rather than the immediate validation path.