fix: bound total decompression under each top-level archive

the limiter bounds what's held *at once*, and each archive gives its bytes back when it's released. So a recursive bomb (42.zip shape) never trips a limit: every level fits on its own, and the scan just runs for effectively forever. Capping each archive at N× its own size wouldn't help either, since every level of such a bomb is high-ratio, so the work still grows about N-fold per level.

- each top-level archive gets one decompression budget of `max(100 × its size, 1 GiB)`, spent by every archive nested under it at any depth
- the budget is attached to the context when the walk enters a top-level archive, so `Extract` picks it up without a signature change
- once it's spent, the archive being extracted is truncated with a "possible decompression bomb" unknown and the walk moves on. The next top-level archive starts fresh

real trees (a war of jars, a layer of tarballs) expand a few times over, well under the ratio.

Signed-off-by: Alex Goodman <wagoodman@users.noreply.github.com>

internal/archive/extract.go

@@ -152,6 +152,10 @@ func (r *Resolver) extract(ctx context.Context, format archives.Extractor, conte
 		r.truncate("extraction stopped at the configured memory or disk limit")
 		return nil
 	}
+	if errors.Is(err, errBudgetSpent) {
+		r.truncate("extraction stopped: the archive and those nested in it decompressed to far more than its size (possible decompression bomb)")
+		return nil
+	}
 	return err
 }