Fix firmware sample and document core generation

docs/README.md

@@ -51,7 +51,7 @@ Assuming the `deviceMetadata` object loaded above is available, device firmware
 ```csharp
 ...
 using var reader = new StreamReader("ios.yml");
-var portPinMetadata = MetadataDeserializer.Instance.Deserialize<PortPinMetadata>(reader);
+var portPinMetadata = MetadataDeserializer.Instance.Deserialize<Dictionary<string, PortPinInfo>>(reader);
 var generator = new FirmwareGenerator(deviceMetadata, portPinMetadata);
 
 var headers = generator.GenerateHeaders();

src/Interface.cs

@@ -58,6 +58,10 @@ public class DeviceMetadata
     /// <summary>
     /// Gets a value indicating whether the metadata describes an application device.
     /// </summary>
+    /// <remarks>
+    /// Metadata declaring no device name describes the core register set. In this case, the
+    /// generated interface carries the register classes and the address map only.
+    /// </remarks>
     [YamlIgnore]
     public bool IsApplicationDevice => !string.IsNullOrEmpty(Device);
 }

src/InterfaceGenerator.cs

@@ -7,6 +7,10 @@ namespace Harp.Generators;
 /// <summary>
 /// Provides automatic generation of reactive device interface implementations.
 /// </summary>
+/// <remarks>
+/// Metadata declaring no device name generates no asynchronous device interface, so
+/// enumerating the result yields a single file.
+/// </remarks>
 public sealed class InterfaceGenerator
 {
     readonly Device _deviceTemplate = new();