fix: disable test harness for no_std binaries, fix shutdown to best-effort notify-and-halt, use CapSlot newtypes

crates/apps/hello/Cargo.toml

@@ -3,6 +3,11 @@ name = "hello"
 version = "0.1.0"
 edition = "2024"
 
+[[bin]]
+name = "hello"
+test = false
+bench = false
+
 [dependencies]
 userspace = { workspace = true }