Classify FAT containers using shared architecture, range, and observed slice-header facts rather than the CAFEBABE signature alone. Preserve typed unsupported and malformed reasons, reject malformed sibling slices consistently, and remove repeated range parsing in consumers.
Validation: valid small and large JVM classes in public JAR/ZIP inspection, four FAT width/byte-order controls, and focused executable/Mach-O boundary tests. The class fixtures were checked with JDK javap; no new JVM analysis capability is advertised.
The Apple selection and Hopper readers retain their existing parsing because they also own oversized-count diagnostics, reserved fields, streaming final-size validation, or source freshness that the shared header result does not represent.
Representative public mixed-ZIP inventory probe, four fresh processes with an already warm filesystem cache: first process elapsed 626.8 -> 548.3 ms, CPU 740 -> 740 ms, sampled family peak RSS 375.5 -> 345.4 MiB. Subsequent three-process medians: elapsed 767.2 -> 454.0 ms, CPU 890 -> 640 ms, peak RSS 368.7 -> 346.2 MiB. Estimated output tokens 2310 -> 2292. Concurrent load was uncontrolled, so these observations do not establish a speed improvement. Whole-agent task tokens and schema/call overhead were not measured.
Fixes#2317
morluto