Every _core.* call previously re-decompressed the archive (≈1.4 s
overhead per call on a 128 MB Sannergata RIV). Decompress once to a
tempfile keyed by (canonical path, mtime_ns); reuse it for every
subsequent Rust call. index_ifc on Sannergata: 2.35 s → 0.98 s
(~2.4× per call). Typical pipeline saves ~4 s per ifczip file.