Pausa: 11 crates del fractal Ente #0 con cerebro completo

PID 1 boot + bus interno autenticado + cerebro KCL/Rust:
- 6 lib crates de infra (card, bus, cas, kernel, soma, wasm, snapshot)
- ente-brain: motor de reglas O(1), observer Shannon, cristalización,
  audit hash-chain, persistencia rules.k, Prometheus /metrics
- KCL schemas card.k + rule.k como gramática autoritativa
- compat-logind D-Bus, ente-echo demo provider, ente-zero PID 1
- 22 tests OK, ~3.8k LOC Rust + ~300 LOC KCL

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/ente-echo/Cargo.toml

@@ -0,0 +1,22 @@
+[package]
+name = "ente-echo"
+version = "0.0.1"
+edition.workspace = true
+license.workspace = true
+publish.workspace = true
+
+[lib]
+name = "ente_echo"
+path = "src/lib.rs"
+
+[[bin]]
+name = "ente-echo"
+path = "src/main.rs"
+
+[dependencies]
+ente-card = { path = "../ente-card" }
+ente-bus = { path = "../ente-bus" }
+anyhow = { workspace = true }
+tokio = { workspace = true }
+tracing = { workspace = true }
+tracing-subscriber = { workspace = true }

crates/ente-echo/src/lib.rs

@@ -0,0 +1,18 @@
+//! Constantes públicas del Ente echo. Lib aparte del bin para que `busctl`
+//! y otros consumidores puedan importar el InterfaceId sin enlazar el binario.
+
+use ente_card::{Capability, InterfaceId};
+
+/// UUID estable del interface "echo". Genera nuevo por sed si forkeas.
+pub const ECHO_IFACE: InterfaceId = InterfaceId([
+    0xec, 0x40, 0xa1, 0x00, 0x00, 0x00, 0x00, 0x01,
+    0x80, 0x00, 0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe,
+]);
+pub const ECHO_VERSION: u16 = 1;
+
+pub fn echo_capability() -> Capability {
+    Capability::Endpoint {
+        interface: ECHO_IFACE,
+        version: ECHO_VERSION,
+    }
+}

crates/ente-echo/src/main.rs

@@ -0,0 +1,46 @@
+//! ente-echo: Ente proveedor mínimo. Anuncia Capability::Endpoint(ECHO) y
+//! responde a invokes echando el blob recibido. Vehículo para validar el
+//! forwarding bus → proveedor → bus → originator.
+
+use ente_bus::{BusResponse, BusServer, InvokeHandler};
+use ente_card::Capability;
+use ente_echo::{echo_capability, ECHO_IFACE, ECHO_VERSION};
+use tracing::{info, warn};
+use tracing_subscriber::EnvFilter;
+
+struct EchoHandler;
+
+impl InvokeHandler for EchoHandler {
+    fn handle(&mut self, cap: Capability, blob: Vec<u8>) -> BusResponse {
+        match cap {
+            Capability::Endpoint { interface, version }
+                if interface == ECHO_IFACE && version == ECHO_VERSION =>
+            {
+                let preview = String::from_utf8_lossy(&blob).into_owned();
+                info!(text = %preview, len = blob.len(), "echo invoke");
+                BusResponse::Invoked { result: blob }
+            }
+            other => {
+                warn!(?other, "ente-echo: capacidad no soportada");
+                BusResponse::Error("ente-echo solo maneja ECHO_IFACE".into())
+            }
+        }
+    }
+}
+
+#[tokio::main(flavor = "current_thread")]
+async fn main() -> anyhow::Result<()> {
+    let filter = EnvFilter::try_from_default_env()
+        .unwrap_or_else(|_| EnvFilter::new("ente_echo=info"));
+    tracing_subscriber::fmt().with_env_filter(filter).with_target(true).init();
+
+    info!("ente-echo arrancando");
+    let mut server = BusServer::from_env().await?;
+    server.announce(vec![echo_capability()]).await?;
+    info!("Announce OK, sirviendo invokes");
+
+    if let Err(e) = server.serve(EchoHandler).await {
+        warn!(?e, "serve terminó");
+    }
+    Ok(())
+}