🔧 Fix peek expression terminator issues and add ternary operator support

- Fix LLVM IR terminator missing in peek expression entry blocks
- Add proper jump instructions between peek blocks
- Implement ternary operator (? :) as syntactic sugar for peek
- Update Python LLVM externcall handling for improved compatibility
- Add comprehensive test cases for peek and ternary expressions
- Update language guide with ternary operator documentation

ChatGPTが頑張って修正してくれたにゃ！🐱

Co-Authored-By: ChatGPT <noreply@openai.com>

src/parser/expressions.rs

@@ -98,7 +98,7 @@ impl NyashParser {
                 condition: Box::new(cond),
                 then_body: vec![then_expr],
                 else_body: Some(vec![else_expr]),
-                span: Span::Unknown,
+                span: Span::unknown(),
             });
         }
         Ok(cond)