[SuperPiIot]

Fixes #4464

Summary

• Add PIPE_PRELUDE in hy-emit providing hy_send_cap[t any] (.send, .close), hy_recv_cap[t any] (.recv, .drain), and hy_pipe[t any](cap ...int) when pipe capabilities are used, while omitting "hy" from emitted Go imports.
• Lower unshadowed hy.pipe[T](...) and hy.new_pipe[T](...) calls in expr.rs to hy_pipe[...](...), map hy.send_cap / hy.recv_cap Go type names and BindingKind::Chan provenance in lib.rs / stmt.rs (for for r in rx, select, closures, and typed var bindings).
• Add integration tests in compiler/crates/hy-emit/tests/hy_pipe_capabilities_4464.rs (including go run -race) and ACCEPT corpus fixture tests/checker-corpus/hy-pipe-capabilities-accept.hy, updating corpus census surfaces (139 -> 140, ACCEPT 45 -> 46).

Verification

• cargo test -p hy-emit --test hy_pipe_capabilities_4464: 4 passed, 0 failed (includes go run -race)
• cargo test -p hy-diag -p hy-syntax -p hy-check -p hy-emit: 3217 passed, 0 failed
• python3 tools/corpus_harness.py --bin target/debug/hyb: verdict agreement 140/140 (tripwire: not fired)
• python3 tools/differential_loop.py --bin target/debug/hyb: accept-side (build+run) 48/48, reject-side (checker) 92/92 (FULL AGREEMENT)
• hyb build --race tests/checker-corpus/hy-pipe-capabilities-accept.hy built and exited 0 (3 9)
• python3 tools/check_corpus_census.py, check_guarantees.py, check_test_registration.py, check_conflict_markers.py, check_claims_links.py: OK

Settlement Coords

• Network: Base Mainnet (Chain ID 8453)
• Asset: USDC
• Address: 0xf084cF0076F91AA48C2370F427C399dAA8C1f07F