Phase 0: bootstrap Rust workspace

- Cargo workspace with 6 crates: shared, storaged, catalogd, queryd, aibridge, gateway
- shared: types (DatasetId, ObjectRef, SchemaFingerprint, DatasetManifest) + error enum
- gateway: Axum HTTP entrypoint with nested service routers + tracing
- All services expose /health stubs
- justfile with build/test/run recipes
- PRD, phase tracker, and ADR docs

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

crates/shared/src/errors.rs

@@ -0,0 +1,35 @@
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum LakehouseError {
+    #[error("dataset not found: {0}")]
+    DatasetNotFound(String),
+
+    #[error("object not found: {bucket}/{key}")]
+    ObjectNotFound { bucket: String, key: String },
+
+    #[error("storage error: {0}")]
+    Storage(String),
+
+    #[error("catalog error: {0}")]
+    Catalog(String),
+
+    #[error("query error: {0}")]
+    Query(String),
+
+    #[error("ai bridge error: {0}")]
+    AiBridge(String),
+
+    #[error("serialization error: {0}")]
+    Serialization(String),
+}
+
+impl LakehouseError {
+    pub fn status_code(&self) -> u16 {
+        match self {
+            Self::DatasetNotFound(_) | Self::ObjectNotFound { .. } => 404,
+            Self::Storage(_) | Self::Catalog(_) | Self::Query(_) | Self::AiBridge(_) => 500,
+            Self::Serialization(_) => 400,
+        }
+    }
+}

crates/shared/src/lib.rs

@@ -0,0 +1,2 @@
+pub mod types;
+pub mod errors;

crates/shared/src/types.rs

@@ -0,0 +1,42 @@
+use serde::{Deserialize, Serialize};
+use uuid::Uuid;
+
+/// Unique identifier for a dataset in the catalog.
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+pub struct DatasetId(pub Uuid);
+
+impl DatasetId {
+    pub fn new() -> Self {
+        Self(Uuid::new_v4())
+    }
+}
+
+impl std::fmt::Display for DatasetId {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+/// Pointer to an object in storage. This is what the catalog stores — never raw data.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ObjectRef {
+    pub bucket: String,
+    pub key: String,
+    pub size_bytes: u64,
+    pub created_at: chrono::DateTime<chrono::Utc>,
+}
+
+/// Schema fingerprint — deterministic hash of an Arrow schema.
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
+pub struct SchemaFingerprint(pub String);
+
+/// Dataset manifest — the catalog's view of a dataset.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct DatasetManifest {
+    pub id: DatasetId,
+    pub name: String,
+    pub schema_fingerprint: SchemaFingerprint,
+    pub objects: Vec<ObjectRef>,
+    pub created_at: chrono::DateTime<chrono::Utc>,
+    pub updated_at: chrono::DateTime<chrono::Utc>,
+}