follow-up to 1eec324 (fix UAF: dupe FrameWork.hostname per submit). the dupe-at-submit logic was inline in FrameHandler.onMessage, which made it hard to regression-test the invariant. extracted a small Subscriber method that returns a FrameWork with heap-owned data + hostname, and added a unit test that: - builds a FrameWork from a to-be-freed hostname buffer - asserts the returned slices have distinct pointers from the inputs - simulates slurper.runWorker teardown by freeing the source hostname - reads the FrameWork.hostname again — would trip the testing allocator's use-after-free detection if the dupe was elided no behavior change at the submit site. tested via zig build test.