GHSA-x494-mj8g-cj27: gix-pack has multiple DoS vectors: unchecked indexing panics and uncapped OOM allocations from crafted pack data

Multiple denial-of-service vectors in gix-pack: unchecked array indexing causes panics on crafted delta data, and uncapped attacker-controlled size headers enable OOM process kills. Both are triggered by malicious pack data received during clone/fetch.