Add type annotations to remaining untyped spec params

trampoline (eval.sx), signal/deref (signals.sx), aser (adapter-sx.sx).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/sx/ref/signals.sx

@@ -42,7 +42,7 @@
 ;; --------------------------------------------------------------------------
 
 (define signal
-  (fn (initial-value)
+  (fn ((initial-value :as any))
     (make-signal initial-value)))
 
 
@@ -55,7 +55,7 @@
 ;; the current value — no subscription, no overhead.
 
 (define deref
-  (fn (s)
+  (fn ((s :as any))
     (if (not (signal? s))
       s  ;; non-signal values pass through
       (let ((ctx (get-tracking-context)))