core: guard extraction against decompression bombs (size/ratio/count limits)

[otsobide]

docs/security.md lists decompression bombs as a currently unmitigated limitation: a tiny archive can expand to enormous data and exhaust disk or memory during extract. This adds the standard output-budget defense to collapse-core extraction.

Scope

• Total output cap — track bytes written across the whole extraction; abort with a clear error when a limit is exceeded.
• Ratio cap — abort when output/input ratio is implausibly high (bombs run 1000:1+; legit archives rarely exceed ~100:1). Uses the per-entry compressed/uncompressed sizes the formats expose.
• Entry-count cap — abort on archives with an absurd number of entries (the "millions of tiny files" variant).
• Limits should be configurable, with safe defaults.

Implementation notes

• zip / 7z: we already control the per-entry extraction loop (extract_zip; extract_7z via decompress_with_extract_fn), so wrap each entry reader in a bounded/counting reader (Read::take) and abort mid-stream.
• Enforce on actual bytes read, not the declared header size — a bomb can declare a small size and deliver gigabytes.
• Stream instead of buffering — extraction currently read_to_ends each entry into memory before writing, so a huge entry exhausts RAM before any disk cap triggers; switch to a streaming copy that counts as it goes. This is the main piece of work.
• tar is a near-non-issue (uncompressed container, ratio ~1:1); only the entry-count / total-size cap is relevant, and we do not support .tar.gz.
• Not affected: recursive/nested bombs (we only extract one level) and overlapping-entry tricks (a total-bytes cap defends against the effect regardless).

Acceptance criteria

• Extraction aborts cleanly (no partial escape, clear error) when the size/ratio/entry-count limits are exceeded, for zip and 7z.
• Limits are enforced on bytes actually read, via streaming (no whole-entry buffering of untrusted input).
• Tests in tests/core/tests/security.rs cover a crafted high-ratio archive and an excessive-entry-count archive.
• docs/security.md updated: move decompression bombs from "known limitations" to a documented measure.

Related: docs/security.md.