feat: lower SQL through unified operators and scalars

Cargo.toml

@@ -2,6 +2,7 @@
 members = [
     "crates/asap-physical-operators",
     "crates/types",
+    "crates/frontend-common",
     "crates/sql-function-catalog",
     "crates/asap-aware-mapping",
     "crates/frontend-promql",

crates/frontend-common/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "asap-frontend-common"
+version = "0.1.0"
+edition = "2021"
+
+# Shared front-end layer: the name-based `UnresolvedOp` tree every front end
+# emits, and the resolver that binds it into the unified `OperatorNode` IR.
+[dependencies]
+asap-types = { path = "../types" }
+serde = { version = "1", features = ["derive", "rc"] }
+thiserror = "2"

crates/frontend-common/src/lib.rs

@@ -0,0 +1,23 @@
+//! `asap-frontend-common` — the front-end-facing, name-based operator tree
+//! and its resolver into the unified IR.
+//!
+//! A front end builds an [`UnresolvedOp`] tree (column references are
+//! name-based [`ColumnRef`](asap_types::pre_asap::ColumnRef)s) during its
+//! own `interpret` step and calls [`resolve_root`], which binds every
+//! reference to a positional `ColumnId` and returns the
+//! [`OperatorNode`](asap_types::ir::OperatorNode) DAG.
+//!
+//! - [`unresolved`] — [`UnresolvedOp`] / [`UnresolvedScalar`]: the tree.
+//! - [`schema_resolver`] — [`SchemaResolver`]: builds the binding schema of a
+//!   schemaless (PromQL) leaf from the names the query references.
+//! - [`resolve`] — [`resolve_root`]: the bottom-up binding walk.
+
+pub mod resolve;
+pub mod schema_resolver;
+pub mod unresolved;
+
+pub use resolve::{resolve_expr, resolve_root, resolve_scalar_root, ResolveDAGError};
+pub use schema_resolver::{SchemaCatalog, SchemaResolver, UsageDerivedCatalog};
+pub use unresolved::{
+    UnresolvedOp, UnresolvedPredicate, UnresolvedProjectItem, UnresolvedScalar, UnresolvedSortKey,
+};