Add durable manifest-rooted result inventories

crates/remora-target/src/store.rs

@@ -258,6 +258,19 @@ impl TargetStore {
         })
     }
 
+    /// Stream and independently hash an exact identity without buffering it.
+    pub async fn verify_exact(
+        &self,
+        identity: &ObjectIdentity,
+    ) -> Result<ObjectMetadata, TargetError> {
+        let (content_sha256, size) = self.hash_exact(identity).await?;
+        Ok(ObjectMetadata {
+            identity: identity.clone(),
+            content_sha256: Some(content_sha256),
+            size,
+        })
+    }
+
     /// Issue a time-limited URL bound to one exact object identity.
     pub async fn presign_read(
         &self,