fix(js): CryptoKey clone hook honours the structuredClone seen map (#423) (#425)

_structuredClone dispatches platform-object hooks as hook(value, seen), but the
CryptoKey hook took only `src` and never touched the memo, and hook branches
return before the generic seen.set. So one CryptoKey referenced twice in a graph
cloned into two distinct objects (and re-registered its key material each time),
where structuredClone preserves reference identity within a graph.

Consult and populate `seen` in the hook. Adds a parity test asserting a key
reached twice clones to one shared object that crypto.subtle still accepts.

crates/obscura-js/js/bootstrap.js

@@ -7094,8 +7094,13 @@ if (!globalThis.crypto.subtle) {
   // _structuredClone via Symbol.toStringTag ("CryptoKey"); registered lazily
   // because structuredClone is defined before this block (issue #389).
   globalThis.__obscura_clone_hooks = globalThis.__obscura_clone_hooks || {};
-  globalThis.__obscura_clone_hooks["CryptoKey"] = function (src) {
+  // `seen` is the clone memo _structuredClone hands every hook. Populate it so
+  // one key reached twice in a graph clones to one shared object (and its key
+  // material is registered once), matching structuredClone's identity rules.
+  globalThis.__obscura_clone_hooks["CryptoKey"] = function (src, seen) {
+    if (seen && seen.has(src)) return seen.get(src);
     const copy = makeKey(src.type, src.extractable, src.algorithm, src.usages, keyBytes(src));
+    if (seen) seen.set(src, copy);
     return copy;
   };