feat(stdlib): annotate all return type and add typed fib bench 🦀

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

Author: timfennis

benches/programs/fibonacci_typed.ndc

@@ -0,0 +1,5 @@
+fn fib(n: Int) -> Int { 
+    if n <= 1 { 1 } else { fib(n - 2) + fib(n - 1) }
+}
+
+fib(26);

ndc_stdlib/src/sequence.rs

@@ -477,6 +477,7 @@ mod inner {
     }
 
     /// Returns `true` if the `predicate` is true for all the elements in `seq`.
+    #[function(return_type = bool)]
     pub fn all(seq: SeqValue, function: &mut VmCallable<'_>) -> anyhow::Result<Value> {
         for item in seq
             .try_into_iter()