Slice prepended scope arg out of user-visible arguments.length

When the scope pass prepends a $$scope argument and toildefender$bind-wraps a
function, user-visible `arguments` must exclude the injected arg. The slice
count was gated on methodRefersToArguments(), which only detects *unresolved*
`arguments` references and misses `arguments.length` (escope resolves
`arguments`). Brand-check helpers (the shape of `#x in obj` / private getters)
then read an off-by-one `arguments.length` and returned the wrong branch,
corrupting downlevelled #private access -- e.g. a WeakMap receiving undefined as
a key. Always slice by the $$scope param count instead.

This is what broke ToilGate's fully-obfuscated build with numeric_vm + dead_code
(dead_code kept the helper native, exposing the path the VM's slice had masked).
Verified end-to-end.

Author: BlobMaster41

src/obfuscator.ts

@@ -798,8 +798,16 @@ export function protect(inputOptions: ToilDefenderOptions): ToilDefenderResult {
             const scopeManager = escope.analyze(ast, lexicalScopeOptions);
             fns = asAstNodeArray(methods.extractMethods(ast));
             fns = fns.map((method: AstNode) => {
-                const refers = methods.methodRefersToArguments(method, scopeManager);
-                const scopeArgumentCount = refers ? nodeParams(method).filter((param) => nodeName(param).indexOf("$$scope") == 0).length : 0;
+                // `bareArguments` (what `arguments` / `arguments.length` lower to) must
+                // be sliced by the number of scope params the scope pass prepended, so
+                // that user-visible `arguments` excludes the injected `$$scope` arg.
+                // This must NOT be gated on methodRefersToArguments(): that helper only
+                // detects *unresolved* `arguments` references, and misses `arguments.length`
+                // (escope resolves `arguments`), which left brand-check helpers like
+                // `#x in obj` reading a length that was off-by-one and returning the wrong
+                // value — corrupting downlevelled #private access. Param-index references
+                // already account for the prepend via the shifted param list.
+                const scopeArgumentCount = nodeParams(method).filter((param) => (nodeName(param) || "").indexOf("$$scope") == 0).length;
                 methods.removeFirstArguments(method, scopeArgumentCount);
                 return asAstNode(methods.replaceArgumentReferences(method, true));
             });