Prune unused code-mode globals (#20542)

Hide Atomics, SharedArrayBuffer, and WebAssembly from the code-mode
runtime since the harness does not expose worker support or need those
APIs.

codex-rs/core/tests/suite/code_mode.rs

@@ -2371,7 +2371,6 @@ text(JSON.stringify(Object.getOwnPropertyNames(globalThis).sort()));
         "Array",
         "ArrayBuffer",
         "AsyncDisposableStack",
-        "Atomics",
         "BigInt",
         "BigInt64Array",
         "BigUint64Array",
@@ -2406,7 +2405,6 @@ text(JSON.stringify(Object.getOwnPropertyNames(globalThis).sort()));
         "Reflect",
         "RegExp",
         "Set",
-        "SharedArrayBuffer",
         "String",
         "SuppressedError",
         "Symbol",
@@ -2421,7 +2419,6 @@ text(JSON.stringify(Object.getOwnPropertyNames(globalThis).sort()));
         "WeakMap",
         "WeakRef",
         "WeakSet",
-        "WebAssembly",
         "__codexContentItems",
         "add_content",
         "decodeURI",