🔧 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/runner/modes/vm.rs

@@ -151,15 +151,14 @@ impl NyashRunner {
                         .status()
                         .map_err(|e| format!("spawn pyvm: {}", e))
                         .unwrap();
+                    // Always propagate PyVM exit code to match llvmlite semantics
+                    let code = status.code().unwrap_or(1);
                     if !status.success() {
-                        eprintln!("❌ PyVM failed (status={})", status.code().unwrap_or(-1));
-                        process::exit(1);
+                        if std::env::var("NYASH_CLI_VERBOSE").ok().as_deref() == Some("1") {
+                            eprintln!("❌ PyVM failed (status={})", code);
+                        }
                     }
-                    // Propagate exit code if set
-                    if let Some(code) = status.code() {
-                        process::exit(code);
-                    }
-                    process::exit(0);
+                    process::exit(code);
                 } else {
                     eprintln!("❌ PyVM runner not found: {}", runner.display());
                     process::exit(1);