🔧 Replace degenerate minimizer logic with hash-based random ordering

- Add `hash` field to MmerItem for stable, randomized minimizer ordering
- Introduce hash_mMER() using mix64 with XOR seed to avoid fixed points (e.g., poly-A/T)
- Remove is_degenerate() and minimizer_worse(), simplifying comparison to hash-only
- Update push logic: compare hashes instead of canonical values with degeneracy checks

.gitignore

@@ -2,3 +2,5 @@
 src/target
 data-stress
 *.fasta
+*.zst
+*.zst.meta