testing/cross_backend/testing_server_deno.ts

Deno runtime adapter for spawnable cross-process test server binaries.

Binds Deno.serve and hono/deno's module-level upgradeWebSocket. The shared testing/cross_backend/testing_server_core.ts owns the rest. Counterpart to testing/cross_backend/testing_server_node.ts — together they isolate the JS-runtime axis (Deno vs Node V8) on identical TS surfaces, and the Rust spine binary covers the cross-language axis.

Deno globals are declared locally (mirroring runtime/deno.ts) so this module typechecks under fuz_app's Node-based config without a deno.json or @types/deno. It is only ever *run* under Deno.