Add compile-time leaf declarations

Introduce a function-like leaf declaration macro, bind endpoint and TUI hosts to shared generated metadata, and move remote shell endpoint construction out of the leaf module into the examples and runtime assembly code.

src/lib.rs

@@ -26,6 +26,6 @@ pub use unshell_protocol as protocol;
 /// Re-export the leaf library crate behind the historical `unshell::leaves` path
 pub use unshell_leaves as leaves;
 
-pub use unshell_macros::{Leaf, Procedure, procedures};
+pub use unshell_macros::{Leaf, Procedure, leaf, procedures};
 
 // pub use ush_obfuscate as obfuscate;