fuzz: add archive_fuzz target

[chaliy]

Summary

Add a fuzz target for the archive builtin (builtins/archive.rs). It handles tar/gzip decompression with zip bomb mitigation — binary format parsers are classic fuzz targets.

Scope

• Fuzz arbitrary binary data as gzip/tar input
• Test decompression ratio checks, malformed headers, truncated archives
• Use libfuzzer's Arbitrary trait for structured binary data

Priority

Medium — binary format decompression with zip bomb edge cases.