[yapishu]

Repeated transaction construction in WebAssembly exhausts memory because Memory::Malloc owns a raw allocation without releasing it. Each temporary Tip5 hashing context allocates an 8 MiB Nock VM stack. Drop now frees malloc-backed storage using the allocation’s original size and alignment; mmap-backed storage uses MmapMut’s destructor.

The regression test tracks outstanding stack allocations across 32 create/drop cycles. It fails with the destructor removed and passes with the fix.

Validation:

• cargo +nightly-2025-02-14 test -p tx-types passes.
• Nockster’s browser test constructs and verifies 32 multi-input bridge drafts using the patched WASM dependency; it passes without exhausting memory.