feat(artifacts): add immutable artifact store

crates/crank-artifacts/src/lib.rs

@@ -0,0 +1,23 @@
+//! A small, Linux-only immutable content-addressed artifact store.
+//!
+//! The directory file descriptor opened by [`ArtifactStore::open`] is the
+//! authority for all operations. Paths supplied by callers are never used for
+//! blob I/O, and the public API deliberately exposes only opaque digests.
+
+#[cfg(not(target_os = "linux"))]
+compile_error!("crank-artifacts requires Linux");
+
+mod error;
+mod housekeeping;
+mod legacy;
+mod model;
+mod store;
+
+#[cfg(debug_assertions)]
+#[doc(hidden)]
+pub mod test_support;
+
+pub use error::ArtifactError;
+pub use housekeeping::{StaleTemp, TempScan};
+pub use model::{ArtifactRef, MAX_ARTIFACT_BYTES, MAX_SOURCE_BYTES, StoredArtifact};
+pub use store::ArtifactStore;