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/storage.go

@@ -43,6 +43,9 @@ func (r *Resolver) put(b *blob, content io.Reader) error {
 	for {
 		n, readErr := content.Read(r.chunk)
 		if n > 0 {
+			if !r.budget.take(int64(n)) {
+				return errBudgetSpent
+			}
 			if err := r.write(b, r.chunk[:n]); err != nil {
 				return err
 			}