feat: resumable sha256 embedding cache + cost estimate

tests/embed_tests.rs

@@ -0,0 +1,28 @@
+use alpha_id::embed::{EmbeddingStore, estimate};
+
+#[test]
+fn cache_key_is_stable_sha256() {
+    let k1 = EmbeddingStore::key("BAAI/bge-m3", "diabetes");
+    let k2 = EmbeddingStore::key("BAAI/bge-m3", "diabetes");
+    assert_eq!(k1, k2);
+    assert_ne!(k1, EmbeddingStore::key("BAAI/bge-m3", "hypertonie"));
+    assert_eq!(k1.len(), 64); // hex sha256
+}
+
+#[test]
+fn store_persists_and_reloads_vectors_resumably() {
+    let dir = tempfile::tempdir().unwrap();
+    let store = EmbeddingStore::open(dir.path().to_str().unwrap(), "BAAI/bge-m3").unwrap();
+    assert!(store.get("diabetes").is_none());
+    store.put("diabetes", &[0.1, 0.2, 0.3]).unwrap();
+    let reopened = EmbeddingStore::open(dir.path().to_str().unwrap(), "BAAI/bge-m3").unwrap();
+    assert_eq!(reopened.get("diabetes").unwrap(), vec![0.1, 0.2, 0.3]);
+    assert!(reopened.has("diabetes"));            // resume: skip already-embedded
+}
+
+#[test]
+fn estimate_reports_pending_count_and_chars() {
+    let est = estimate(&["abc".to_string(), "de".to_string()]);
+    assert_eq!(est.items, 2);
+    assert_eq!(est.chars, 5);
+}