Classify typed drag and download APIs as independent native host services #625

Problem

Current WebScene main c57d82dfef38c8e18eb691d54d3132851e34025a fails CI run 35430278924 on Linux and macOS in tooling/webscene/tests/native-binary-interop.test.mjs.

The contract classifies every versioned v1/v2 symbol outside independentHostApis as retired JavaScript invocation transport. Four current host APIs are therefore reported incorrectly:

• webscene_engine_dispatch_drag_v1
• webscene_engine_take_download_request_v1
• webscene_engine_take_outbound_drag_request_v1
• webscene_engine_complete_outbound_drag_v1

These are current typed drag/download host services, not the retired JSON JavaScript invocation ABI.

Proposed fix

Add the four typed host-service symbols to the explicit independent-host allowlist while retaining the broad fail-closed scan for unreviewed v1/v2 JavaScript interop symbols. Record the current-main runner failure and ownership boundary.

Acceptance

• The contract continues to require the ABI v3 leased JavaScript invocation symbols.
• The four typed drag/download host APIs are classified as independent host services in both header and export surfaces.
• Unknown v1/v2 engine/interop symbols still fail the contract.
• Linux and macOS current-main CI no longer fail on these valid host APIs.