Hide raw OpenUSD types from the public USDInterop surface

[elkraneo]

Summary

Deconstructed now builds on the public USDInterop package family, but the public graph still exposes OpenUSD 6.1.0-preflight.1 more than intended.

This is not a business/IP leak. It is an API hygiene and build-friction issue.

Problem

Deconstructed does not publicly export OpenUSD types from its own app-facing modules, but USDInterop still exposes a public shim that uses raw pxr types in public signatures:

• Sources/USDInterop/USDInterop+OpenUSDShim.swift

That keeps OpenUSD visible in the public technical contract even though the intended consumer contract is:

• USDInterfaces
• USDInterop
• USDInteropCxx
• USDOperations

with OpenUSD treated as an implementation dependency of the package family, not as part of the intended app-facing API.

Why this matters

• creates accidental public API commitment to raw pxr types
• increases build and macro-approval friction for downstream consumers
• weakens the cleanliness of the USDOperations / USDTools split

Desired outcome

• keep OpenUSD out of public-facing signatures where possible
• make USDInteropOpenUSDShim internal or otherwise non-consumer-facing if only USDOperations needs it
• preserve the existing functionality while tightening the public contract

Acceptance criteria

• no public USDInterop or USDOperations API exposes raw OpenUSD / pxr types unless there is a deliberate documented exception
• OpenUSD remains an implementation dependency of the USDInterop package family rather than an intended downstream app API surface
• Deconstructed continues to build on the public USDInterop package family without requiring app code to import raw OpenUSD