sausage-plugin part 2: import! with typed clients (sausage_interface::client_rs), TCP endpoints with rpc.endpoint, examples

Part 1 fixes: complete stdout writes, buffered stdin, Rust type names
in schemas, enum variant docs, -32603 for serde errors in handlers,
crate docs and modules. End-to-end check of a generated consumer through
a fake core.

sdk/tests/plugins/consumer/src/main.rs

@@ -0,0 +1,25 @@
+//! Consumer of the probe's actual discovered interface.
+use sausage_plugin::{Result, rpc};
+sausage_plugin::import!("probe");
+struct Consumer;
+#[rpc]
+impl Consumer {
+    /// Route an imported call through the core.
+    async fn run(&self) -> Result<i32> {
+        Ok(probe::add(probe::Add { a: 2, b: 3 })
+            .detach()
+            .on_notify(|name, _| eprintln!("typed progress: {name}"))
+            .await? as i32)
+    }
+    /// Connect to the provider's endpoint and receive its notification.
+    async fn endpoint(&self) -> Result<u64> {
+        let control = probe::control::connect("/endpoint").await?;
+        control
+            .stats()
+            .on_notify(|name, _| eprintln!("endpoint notification: {name}"))
+            .await
+    }
+}
+fn main() {
+    sausage_plugin::run(Consumer)
+}