feat: Introduce Hybrid Logical Clocks in protobuf, update architecture documentation, and add HLC test cases.

lattice-core/src/node.rs

@@ -0,0 +1,30 @@
+//! Node identity and cryptographic keys
+
+use ed25519_dalek::{SigningKey, VerifyingKey};
+use rand::rngs::OsRng;
+
+/// A node in the Lattice mesh.
+///
+/// Each node has an Ed25519 keypair used for signing sigchain entries
+/// and establishing trust within the network.
+pub struct Node {
+    signing_key: SigningKey,
+}
+
+impl Node {
+    /// Generate a new node with a random keypair.
+    pub fn generate() -> Self {
+        let signing_key = SigningKey::generate(&mut OsRng);
+        Self { signing_key }
+    }
+
+    /// Get the node's public key (identity).
+    pub fn public_key(&self) -> VerifyingKey {
+        self.signing_key.verifying_key()
+    }
+
+    /// Get the signing key for creating signatures.
+    pub fn signing_key(&self) -> &SigningKey {
+        &self.signing_key
+    }
+}