feat(typedef): add implementation task decomposition (12 tasks, 7 generations)

Break the alknet-typedef architecture specs into atomic, dependency-ordered
implementation tasks covering crate init, error types, schema layer, data
access, both layout modes (aligned static + packed sequential), TUnion
dispatch, jsonschema custom keyword validators, TypedefEngine integration,
comprehensive tests, and a final review checkpoint.

Validated: 12 tasks, 0 cycles, 7 parallel generations.

tasks/typedef/crate-init.md

@@ -0,0 +1,131 @@
+---
+id: typedef/crate-init
+name: Initialize alknet-typedef crate with Cargo.toml, dependencies, and module skeleton
+status: pending
+depends_on: []
+scope: moderate
+risk: low
+impact: project
+level: implementation
+---
+
+## Description
+
+Initialize the `alknet-typedef` crate from scratch. This is a greenfield crate — the
+binary struct engine that takes a JSON Schema with `TypeDef:*` custom keywords and
+produces an offset map, read/write functions, and validation. The schema is the format
+definition; the engine is generic.
+
+Per [ADR-095](../../docs/architecture/decisions/095-alknet-typedef-purpose-scope-jsonschema-engine.md),
+the crate depends on `jsonschema` (v0.46.5, Draft 2020-12) for validation and
+`serde_json` (with `preserve_order`) for schema parsing. No tokio, no platform deps.
+Compiles to `wasm32-unknown-unknown`.
+
+### Crate setup
+
+Create `crates/alknet-typedef/` with:
+
+- `Cargo.toml` — package metadata, dependencies
+- `src/lib.rs` — crate root with module declarations and re-exports
+- Module skeleton files for:
+  - `src/error.rs` — `TypedefError` enum (ADR-098)
+  - `src/schema.rs` — TypeDef kind detection, annotation parsing, `$ref` normalization, `Endian` enum (ADR-097)
+  - `src/data_access.rs` — primitive read/write functions for all 17 TypeDef kinds
+  - `src/offset_map.rs` — aligned static `OffsetMap` computation (ADR-096 Mode 2)
+  - `src/layout_builder.rs` — packed sequential `LayoutBuilder` (ADR-096 Mode 1, write side)
+  - `src/sequential_reader.rs` — packed sequential `SequentialReader` (ADR-096 Mode 1, read side)
+  - `src/tunion.rs` — TUnion discriminator dispatch (byte-offset and field-name, ADR-097 §4)
+  - `src/validation.rs` — custom keyword validators for all 17 `TypeDef:*` kinds
+  - `src/engine.rs` — `TypedefEngine` struct combining layout + validator
+
+### Dependencies
+
+Per the architecture spec ([overview.md](../../docs/architecture/crates/typedef/overview.md)):
+
+| Crate | Purpose |
+|-------|---------|
+| `jsonschema` 0.46 | Validation engine, custom keyword support (workspace path: `../../jsonschema`) |
+| `serde_json` (preserve_order) | Schema parsing; field order is load-bearing for binary layouts |
+
+No other dependencies. No tokio, no platform deps.
+
+### Workspace Cargo.toml
+
+Add `crates/alknet-typedef` to the workspace `members` list in the root `Cargo.toml`.
+
+### Module skeleton
+
+```rust
+// src/lib.rs
+//! alknet-typedef: The binary struct engine.
+//!
+//! Takes a JSON Schema with `TypeDef:*` custom keywords and produces
+//! an offset map, read/write functions, and validation — all driven
+//! by the schema. The schema is the format definition; the engine is
+//! generic.
+//!
+//! ## Architecture
+//!
+//! - **Schema layer** ([`schema`]): TypeDef kind detection, annotation
+//!   parsing, `$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;
+
+// Re-exports (filled in by subsequent tasks)
+```
+
+Each module file gets a doc comment and `// TODO: implement` marker.
+
+## Acceptance Criteria
+
+- [ ] `crates/alknet-typedef/Cargo.toml` exists with `jsonschema` and `serde_json` (preserve_order) dependencies
+- [ ] `jsonschema` dependency uses workspace path (`path = "../../jsonschema"`) or git/crates.io as appropriate
+- [ ] `crates/alknet-typedef/src/lib.rs` exists with module declarations for all 9 modules
+- [ ] Module skeleton files exist: `error.rs`, `schema.rs`, `data_access.rs`, `offset_map.rs`, `layout_builder.rs`, `sequential_reader.rs`, `tunion.rs`, `validation.rs`, `engine.rs`
+- [ ] Root `Cargo.toml` `members` list includes `crates/alknet-typedef`
+- [ ] `cargo check -p alknet-typedef` succeeds
+- [ ] `cargo clippy -p alknet-typedef` succeeds with no warnings
+- [ ] Dual licensing: `MIT OR Apache-2.0` (workspace-inherited)
+- [ ] No tokio dependency (WASM-clean by construction)
+- [ ] `serde_json` has `preserve_order` feature enabled
+- [ ] `cargo build --workspace` still succeeds (old code untouched)
+
+## References
+
+- docs/architecture/crates/typedef/README.md — crate overview and design principles
+- docs/architecture/crates/typedef/overview.md — purpose, dependencies, scope boundaries
+- docs/architecture/decisions/095-alknet-typedef-purpose-scope-jsonschema-engine.md — ADR-095
+- docs/research/alknet-typedef/findings.md — POC results
+- /workspace/jsonschema/ — the jsonschema crate (v0.46.5)
+- /workspace/alknet-typedef-poc/ — POC code (disposable reference)
+
+## Notes
+
+> This is the foundational setup task for alknet-typedef. All subsequent typedef/*
+> tasks depend on this one. The crate is dependency-light: `jsonschema` + `serde_json`
+> only. No tokio, no platform deps — WASM-clean by construction. The `jsonschema` crate
+> is already in the workspace at `/workspace/jsonschema/` but not yet used by any
+> alknet crate — typedef is the first consumer.
+
+## Summary
+
+> To be filled on completion