feat: allow empty argument list methods in calls, definitions, and docs

- Compile empty `()` as a valid method signature distinct from no parentheses
- Update `call()`, `clear()`, `run()`, `try()`, and `yield()` to use empty argument lists
- Revise documentation across multiple files to reflect new signature semantics

doc/site/lists.markdown

@@ -106,5 +106,5 @@ The `removeAt` method returns the removed item:
 If you want to remove everything from the list, you can clear it:
 
     :::dart
-    hirsute.clear
+    hirsute.clear()
     IO.print(hirsute) // []