security: bound ZIP/NPZ member decompression

[Pyhroff]

Summary

• Bound ZIP/NPZ archive member count, per-member decompressed bytes, and aggregate decompressed bytes.
• Replace whole-member ZipFile.read() with bounded streaming reads.
• Treat oversized entries, archive read failures, and resource-limit hits as suspicious parse errors (MEDIUM), not silently safe.
• Add self-test regression coverage for per-member and aggregate limits.

Scope

This is separate from PR #5's NumPy header parser change; it hardens ZIP container handling only. The scanner still never deserializes pickle payloads.

Validation

The existing self-test workflow should validate the changes. No security checks are disabled or weakened; this PR is not merged automatically.