console: one sequential loop; host tests in one binary

The console reads a line, runs it to the end, and prints the result,
with and without a terminal. Notifications print while a command runs.
Ctrl-C during a command stops only the wait. 314 lines (was 480).

All host integration tests are modules of cli/tests/host/, so they run
in one parallel pool, and the probes build once. Warm, the 184 host
tests take 24 s (was about 45 s as seven binaries in sequence), and
cargo test --workspace takes 45 s.

cli/tests/host/common.rs

@@ -0,0 +1,43 @@
+//! Persistent caches and guest builds shared by the host integration modules.
+use std::{
+    path::{Path, PathBuf},
+    sync::OnceLock,
+};
+
+pub const CACHE: &str = concat!(env!("CARGO_TARGET_TMPDIR"), "/cache");
+
+pub fn build(package: &str, binary: &str) -> PathBuf {
+    let root = Path::new(env!("CARGO_MANIFEST_DIR")).parent().unwrap();
+    let target = Path::new(concat!(env!("CARGO_TARGET_TMPDIR"), "/guests"));
+    assert!(
+        std::process::Command::new("cargo")
+            .args([
+                "build",
+                "--offline",
+                "--target",
+                "wasm32-wasip2",
+                "--manifest-path"
+            ])
+            .arg(root.join(package).join("Cargo.toml"))
+            .arg("--target-dir")
+            .arg(target)
+            .status()
+            .unwrap()
+            .success()
+    );
+    target
+        .join("wasm32-wasip2/debug")
+        .join(format!("{binary}.wasm"))
+}
+
+pub fn probe() -> PathBuf {
+    static WASM: OnceLock<PathBuf> = OnceLock::new();
+    WASM.get_or_init(|| build("cli/tests/plugins/probe", "probe"))
+        .clone()
+}
+
+pub fn sdk_probe() -> PathBuf {
+    static WASM: OnceLock<PathBuf> = OnceLock::new();
+    WASM.get_or_init(|| build("sdk/tests/plugins/probe", "sdk-probe"))
+        .clone()
+}