feat(typedef/crate-init): initialize alknet-typedef crate skeleton

Created crates/alknet-typedef/ with Cargo.toml depending on jsonschema 0.46
(default-features = false for WASM-cleanliness) and serde_json with
preserve_order. Added src/lib.rs with module declarations for all 9 modules
and skeleton source files for each. Added crate to workspace members list.

Verified: cargo check, clippy -D warnings, and build --workspace all succeed.
Dependency tree confirmed free of tokio/reqwest/rustls (WASM-clean).

crates/alknet-typedef/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "alknet-typedef"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+description = "Binary struct engine: takes a JSON Schema with TypeDef:* custom keywords and produces an offset map, read/write functions, and validation"
+repository.workspace = true
+
+[lib]
+name = "alknet_typedef"
+
+[features]
+default = []
+
+[dependencies]
+jsonschema = { version = "0.46", default-features = false }
+serde_json = { version = "1", features = ["preserve_order"] }

crates/alknet-typedef/src/data_access.rs

@@ -0,0 +1,4 @@
+//! Data access layer: primitive read/write functions for all 17 TypeDef
+//! kinds with endianness support, bounds checking, and zero-copy access.
+
+// TODO: implement

crates/alknet-typedef/src/engine.rs

@@ -0,0 +1,7 @@
+//! `TypedefEngine` — the compiled form of a schema.
+//!
+//! Combines the layout engine (both packed and aligned modes) and the
+//! jsonschema validator into a single struct. Built once at schema load
+//! time via [`TypedefEngine::compile`].
+
+// TODO: implement

crates/alknet-typedef/src/error.rs

@@ -0,0 +1,7 @@
+//! Error types for the typedef engine.
+//!
+//! Decided in ADR-098: a single `TypedefError` enum covers all error
+//! conditions across the engine's three phases (schema parsing, offset
+//! computation, read/write) plus validation.
+
+// TODO: implement

crates/alknet-typedef/src/layout_builder.rs

@@ -0,0 +1,9 @@
+//! Packed sequential `LayoutBuilder` — Mode 1 write-side (ADR-096).
+//!
+//! Fields are packed with no alignment padding. Variable-length fields
+//! shift all subsequent fields. The consumer provides actual data sizes
+//! for variable-length fields; the builder computes byte positions for
+//! each field. Used at write time when the consumer knows the data sizes
+//! upfront.
+
+// TODO: implement

crates/alknet-typedef/src/lib.rs

@@ -0,0 +1,32 @@
+//! alknet-typedef: The binary struct engine.
+//!
+//! Takes a JSON Schema with `TypeDef:*` custom keywords and produces
+//! an offset map, read/write functions, and validation — all driven
+//! by the schema. The schema is the format definition; the engine is
+//! generic.
+//!
+//! ## Architecture
+//!
+//! - **Schema layer** ([`schema`]): TypeDef kind detection, annotation
+//!   parsing, `$ref` normalization, endianness.
+//! - **Layout engine** ([`offset_map`], [`layout_builder`],
+//!   [`sequential_reader`]): Two layout modes — aligned static for
+//!   mmap-friendly formats, packed sequential for protocol wire formats.
+//! - **Data access** ([`data_access`]): Typed read/write at computed
+//!   offsets, zero-copy for fixed-size types.
+//! - **TUnion dispatch** ([`tunion`]): Byte-offset and field-name
+//!   discriminator dispatch.
+//! - **Validation** ([`validation`]): Custom keyword validators for all
+//!   17 `TypeDef:*` kinds, delegated to the `jsonschema` crate.
+//! - **Engine** ([`engine`]): `TypedefEngine` — the compiled form of a
+//!   schema, combining layout and validation.
+
+pub mod data_access;
+pub mod engine;
+pub mod error;
+pub mod layout_builder;
+pub mod offset_map;
+pub mod schema;
+pub mod sequential_reader;
+pub mod tunion;
+pub mod validation;

crates/alknet-typedef/src/offset_map.rs

@@ -0,0 +1,8 @@
+//! Aligned static `OffsetMap` — Mode 2 of the two layout modes (ADR-096).
+//!
+//! Fields have fixed positions with natural alignment padding.
+//! Variable-length fields get a 4-byte length prefix at a known offset;
+//! the variable data is not included in the static layout. Used for
+//! mmap-friendly formats (metatensor, safetensors).
+
+// TODO: implement

crates/alknet-typedef/src/schema.rs

@@ -0,0 +1,6 @@
+//! Schema layer: TypeDef kind detection, annotation parsing, `$ref`
+//! normalization, and the `Endian` enum.
+//!
+//! Per ADR-097 and the schema-layer spec.
+
+// TODO: implement

crates/alknet-typedef/src/sequential_reader.rs

@@ -0,0 +1,7 @@
+//! Packed sequential `SequentialReader` — Mode 1 read-side (ADR-096).
+//!
+//! Walks a buffer field-by-field according to the schema, reading length
+//! prefixes to determine variable-length data positions. Used at read
+//! time when the consumer is parsing an incoming frame.
+
+// TODO: implement

crates/alknet-typedef/src/tunion.rs

@@ -0,0 +1,7 @@
+//! TUnion discriminator dispatch (ADR-097 §4).
+//!
+//! TUnion supports two discriminator kinds: byte-offset (protocol
+//! dispatch, e.g., SFTP type bytes) and field-name (typedef.ts string
+//! pattern).
+
+// TODO: implement

crates/alknet-typedef/src/validation.rs

@@ -0,0 +1,7 @@
+//! Custom keyword validators for all 17 `TypeDef:*` kinds, registered
+//! via `jsonschema::options().with_keyword(...)`.
+//!
+//! Per ADR-098: the `jsonschema` crate handles all structural validation;
+//! the custom keywords only validate leaf type constraints.
+
+// TODO: implement