Hojun-Cho
0e61db1857
The loud bound (capture dup not yet portable, #35/#34/#7) flips to the real dup now that #35's spread place-chain sources landed: fresh slice header + spread-append, the D3 spelling of Hare's alloc-dup. The ok/defer-if frees drop (free() is the documented no-op, #27). Dup-independence rows drive add_thread directly: values carried, backing independent both directions, empty parent → empty dup.