feat: switch method signatures to parenthesized parameter notation and update error messages

The method signature format has been changed from space-counted arity (e.g., "== ") to explicit parenthesized parameter lists (e.g., "==(_)"). This required updating the MAX_METHOD_SIGNATURE calculation to account for parentheses and parameter separators, replacing the old copyName helper with a new Signature struct and SignatureType enum, and rewriting the methodNotFound error message to display the full signature string instead of reconstructing arity from trailing spaces. All core method registrations in wren_core.c, wren_io.c, and corresponding test expectations have been updated to use the new signature format.

test/fiber/error.wren

@@ -3,5 +3,5 @@ var fiber = new Fiber {
 }
 
 IO.print(fiber.error) // expect: null
-IO.print(fiber.try)   // expect: String does not implement method 'unknown' with 0 arguments.
-IO.print(fiber.error) // expect: String does not implement method 'unknown' with 0 arguments.
+IO.print(fiber.try)   // expect: String does not implement 'unknown'.
+IO.print(fiber.error) // expect: String does not implement 'unknown'.

test/fiber/try.wren

@@ -6,5 +6,5 @@ var fiber = new Fiber {
 
 IO.print(fiber.try)
 // expect: before
-// expect: Bool does not implement method 'unknownMethod' with 0 arguments.
+// expect: Bool does not implement 'unknownMethod'.
 IO.print("after try") // expect: after try