Node: add succinct top-level crate documentation

Author: dannywillems

node/src/lib.rs

@@ -1,3 +1,42 @@
+//! # Node Crate
+//!
+//! The node crate combines all state machines of the Mina blockchain node into
+//! one unified state machine using a Redux-style architecture.
+//!
+//! ## Core Architecture
+//!
+//! | Component   | Location           | Purpose                                      |
+//! |-------------|--------------------|----------------------------------------------|
+//! | Actions     | [`Action`]         | Events that trigger state changes            |
+//! | Effects     | [`effects()`]      | Side-effects and service calls               |
+//! | Reducers    | [`reducer()`]      | Functions that mutate state                  |
+//! | Services    | [`service`]        | I/O and heavy computation (separate threads) |
+//! | State       | [`State`]          | Centralized, immutable data structure        |
+//!
+//! ## Execution Flow
+//!
+//! ```text
+//! Event arrives
+//! -> Dispatch Action
+//! -> Check Enabling Condition
+//! -> Reducer (mutate state)
+//! -> Effects (side-effects)
+//! -> Service callbacks
+//! -> Loop
+//! ```
+//!
+//! ## Key Components
+//!
+//! | Component           | Module                  | Purpose                             |
+//! |---------------------|-------------------------|-------------------------------------|
+//! | Block Producer      | [`block_producer`]      | Block creation on won slots         |
+//! | Ledger              | [`ledger`]              | Account state and transactions      |
+//! | P2P                 | [`p2p`]                 | Networking layer                    |
+//! | RPC                 | [`rpc`]                 | JSON-RPC API                        |
+//! | SNARK Pool          | [`snark_pool`]          | Proof work management               |
+//! | Transaction Pool    | [`transaction_pool`]    | Mempool for pending transactions    |
+//! | Transition Frontier | [`transition_frontier`] | Blockchain consensus and best chain |
+
 #![allow(clippy::if_same_then_else)]
 
 extern crate graphannis_malloc_size_of as malloc_size_of;