Add procedure-scoped stateful leaves

Cargo.toml

@@ -25,6 +25,7 @@ static_init      = "1.0.4"
 syn               = "2.0.117"
 quote             = "1.0.45"
 proc-macro2       = "1.0.106"
+portable-pty      = "0.9.0"
 unshell          = { path = "." }
 # ush-obfuscate = { path = "./ush-obfuscate" }
 # base62        = { path = "./base62" }
@@ -49,6 +50,7 @@ chrono            = { workspace = true, optional = true }
 # ush-obfuscate     = { workspace = true }
 static_init       = { workspace = true }
 unshell-macros    = { path = "./unshell-macros" }
+portable-pty      = { workspace = true }
 
 [[example]]
 name = "leaf_derive"