[core] stop Intercept refusing declarations without a checkReceiver

`Intercept` threw for any declaration that converts IDL arguments and
does not pass a `checkReceiver`. No call site has ever passed one - 19
declarations on develop, zero with a receiver check - so the refusal
fired for every such interface, and `loadModules` swallowed the throw
into a `dbg.error`. Because it aborts the module function, everything
declared after the offending member went with it.

10 of the 19 declarations on develop were being refused: CookieStore,
Document.cookie, History, all five of performance.ts, StorageManager
and FileSystemHandle behind it, and Worklet. The runway failures are a
readout of exactly that set - ckjar-*, cookies-*, the pushstate tests,
platform-performance-observer, platform-resource-timing-own-entries -
none of which fail on 060552a4, before #110 landed.

The ordering it guarded is real: Web IDL brand-checks the receiver
before converting arguments, and conversion runs page code. But the
predicate asked whether a member declares IDL arguments at all, not
whether its conversion can run any page code, so `@Arguments()` with no
types was refused too. And a promise-only interface like Cache or
CookieStore has no member that can satisfy the contract at all, since
they reject rather than throw. Refusing to install is much the worse
outcome: for the storage-shaped modules it means no origin scoping,
which is a cross-origin leak traded for a fingerprint.

#117 tracks the real fix - a predicate that asks whether a conversion
can run page code, an async brand check, and a build-time failure.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_018Zn7Pst62DZXqzGyrkQ68o

packages/scramjet/packages/core/src/client/client.ts

@@ -1177,11 +1177,17 @@ return { apply, construct };
 
 	/**
 	 * `checkReceiver` must synchronously invoke a side-effect-free native getter
-	 * or method on the receiver, throwing for an invalid receiver. It is required
-	 * for instance members with IDL arguments: Web IDL checks the receiver before
-	 * converting arguments. For example, Headers can use the saved `has` method
-	 * with a fixed valid name; Blob can use its saved `size` getter. Merely
-	 * constructing a `client.native` wrapper does not check anything.
+	 * or method on the receiver, throwing for an invalid receiver. Web IDL checks
+	 * the receiver before converting arguments, and conversion runs page code, so
+	 * an instance member with IDL arguments wants one. For example, Headers can
+	 * use the saved `has` method with a fixed valid name; Blob can use its saved
+	 * `size` getter. Merely constructing a `client.native` wrapper does not check
+	 * anything.
+	 *
+	 * Wanted, not required: omitting it leaves the ordering imprecise rather than
+	 * refusing the declaration, because a promise-only interface has no member
+	 * that can satisfy the contract and the interfaces that do are better off
+	 * installed. See #117.
 	 */
 	Intercept(handler: any, checkReceiver?: (receiver: any) => void): void {
 		const foreignbaseclass = Object_getPrototypeOf(handler);
@@ -1198,25 +1204,15 @@ return { apply, construct };
 			Object_getOwnPropertyDescriptors(handler.prototype);
 		const staticDescs: Record<string | symbol, PropertyDescriptor> =
 			Object_getOwnPropertyDescriptors(handler);
-		// Refuse an unsafe declaration before installing any of its members.
-		if (!checkReceiver) {
-			for (const descs of isglobal
-				? [prototypeDescs, staticDescs]
-				: [prototypeDescs]) {
-				for (const key of Reflect_ownKeys(descs)) {
-					const desc = descs[key];
-					if (isConstructorMember(desc.value)) continue;
-					if (
-						memberValidator(this.box, desc.value) ||
-						memberValidator(this.box, desc.set, true)
-					) {
-						throw new Error(
-							`Intercept(${classname}.${String(key)}) requires a native receiver check before IDL conversion`
-						);
-					}
-				}
-			}
-		}
+		// A declaration that converts IDL arguments without a `checkReceiver`
+		// used to be refused here. Nothing has ever passed one, so the refusal
+		// threw for every such interface and `loadModules` swallowed it into a
+		// `dbg.error` - silently uninstalling cookie, CookieStore, history,
+		// performance and opfs, which is a far worse outcome than the argument
+		// conversion ordering it was guarding. See #117 for the real fix: a
+		// predicate that asks whether a conversion can run page code at all, an
+		// async brand check for the promise-only interfaces, and a build-time
+		// failure rather than a runtime one.
 
 		// create a fake parent prototype for the handler, so that `super.method()` calls resolve to the native store versions
 		const fakePrototype = {};