Phase 1: storage + catalog layer

- storaged: object_store backend (LocalFileSystem), PUT/GET/DELETE/LIST endpoints
- shared: arrow_helpers with Parquet roundtrip + schema fingerprinting (2 tests)
- catalogd: in-memory registry with write-ahead manifest persistence to object storage
- catalogd: POST/GET /datasets, GET /datasets/by-name/{name}
- gateway: wires storaged + catalogd with shared object_store state
- Phase tracker updated: Phase 0 + Phase 1 gates passed

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/shared/src/arrow_helpers.rs

@@ -0,0 +1,83 @@
+use arrow::array::RecordBatch;
+use arrow::datatypes::SchemaRef;
+use bytes::Bytes;
+use parquet::arrow::ArrowWriter;
+use parquet::arrow::arrow_reader::ParquetRecordBatchReaderBuilder;
+use sha2::{Digest, Sha256};
+
+use crate::types::SchemaFingerprint;
+
+/// Write a RecordBatch to Parquet bytes.
+pub fn record_batch_to_parquet(batch: &RecordBatch) -> Result<Bytes, String> {
+    let mut buf = Vec::new();
+    let mut writer = ArrowWriter::try_new(&mut buf, batch.schema(), None)
+        .map_err(|e| e.to_string())?;
+    writer.write(batch).map_err(|e| e.to_string())?;
+    writer.close().map_err(|e| e.to_string())?;
+    Ok(Bytes::from(buf))
+}
+
+/// Read Parquet bytes into a Vec of RecordBatches.
+pub fn parquet_to_record_batches(data: &[u8]) -> Result<(SchemaRef, Vec<RecordBatch>), String> {
+    let builder = ParquetRecordBatchReaderBuilder::try_new(Bytes::copy_from_slice(data))
+        .map_err(|e| e.to_string())?;
+    let schema = builder.schema().clone();
+    let reader = builder.build().map_err(|e| e.to_string())?;
+    let batches: Vec<RecordBatch> = reader.collect::<Result<Vec<_>, _>>().map_err(|e| e.to_string())?;
+    Ok((schema, batches))
+}
+
+/// Compute a deterministic fingerprint from an Arrow schema.
+pub fn fingerprint_schema(schema: &SchemaRef) -> SchemaFingerprint {
+    let mut hasher = Sha256::new();
+    for field in schema.fields() {
+        hasher.update(field.name().as_bytes());
+        hasher.update(field.data_type().to_string().as_bytes());
+        hasher.update(if field.is_nullable() { b"1" } else { b"0" });
+    }
+    let hash = hasher.finalize();
+    SchemaFingerprint(format!("{hash:x}"))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use arrow::array::{Float64Array, Int32Array, StringArray};
+    use arrow::datatypes::{DataType, Field, Schema};
+    use std::sync::Arc;
+
+    fn sample_batch() -> RecordBatch {
+        let schema = Arc::new(Schema::new(vec![
+            Field::new("id", DataType::Int32, false),
+            Field::new("name", DataType::Utf8, false),
+            Field::new("score", DataType::Float64, true),
+        ]));
+        RecordBatch::try_new(
+            schema,
+            vec![
+                Arc::new(Int32Array::from(vec![1, 2, 3])),
+                Arc::new(StringArray::from(vec!["alice", "bob", "carol"])),
+                Arc::new(Float64Array::from(vec![9.5, 8.2, 7.8])),
+            ],
+        )
+        .unwrap()
+    }
+
+    #[test]
+    fn roundtrip_parquet() {
+        let batch = sample_batch();
+        let parquet_bytes = record_batch_to_parquet(&batch).unwrap();
+        let (schema, batches) = parquet_to_record_batches(&parquet_bytes).unwrap();
+        assert_eq!(schema.fields().len(), 3);
+        assert_eq!(batches.len(), 1);
+        assert_eq!(batches[0].num_rows(), 3);
+    }
+
+    #[test]
+    fn schema_fingerprint_deterministic() {
+        let batch = sample_batch();
+        let fp1 = fingerprint_schema(&batch.schema());
+        let fp2 = fingerprint_schema(&batch.schema());
+        assert_eq!(fp1, fp2);
+    }
+}

crates/shared/src/lib.rs

@@ -1,2 +1,3 @@
 pub mod types;
 pub mod errors;
+pub mod arrow_helpers;