Build separate native and WASI pipelines with shared multicall names

Checkpoint before integration and package validation.

Assisted-by: SurmAgent:unknown [read] [edit] [bash]

userland/qjs/source/tests/fix_set_array_length-uaf.js

@@ -0,0 +1,6 @@
+// Crash — heap-use-after-free (confirmed with ASan)
+const arr = [{a:1}, {b:2}, {c:3}, {d:4}, {e:5}];
+arr.length = 2;   // frees elements 2-4
+arr.length = 5;   // grows length back; count stays at 2
+arr.push({f:6}); // count jumps to 6; elements 2-4 are freed but readable
+print(JSON.stringify(arr[3])); // reads freed memory