cargo.build, the WASI test runner, the console, and core.notify ordering

- cargo.build (native): one source copy, tests under WASI, release
  build to /state/cargo/builds/<n>/, process groups killed on cancel.
  The host writes the SDK copy to /plugins/cargo/sdk/ at start.
- sausage test-runner: one instance per test, in parallel, with its own
  mount table (empty world, package folder at its path); answers
  core.lock, core.unlock, core.notify, core.log.
- The console: rustyline, notifications while typing, ls/cat through the
  process view, methods, ps, log, activate, revert, stop, kill.
- core.notify on stdout is handled in order, before the response.

cli/tests/crates/cargo-hang/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "cargo-hang"
+version = "0.1.0"
+edition = "2024"
+
+[workspace]

cli/tests/crates/cargo-hang/build.rs

@@ -0,0 +1,7 @@
+//! A build script descendant that stays alive until the native call ends.
+fn main() {
+    std::process::Command::new("sh")
+        .args(["-c", "echo $$ > child.pid; exec sleep 1000"])
+        .status()
+        .unwrap();
+}

cli/tests/crates/cargo-hang/src/main.rs

@@ -0,0 +1 @@
+fn main() {}