feat: add Console.readLine and Console.readInt, guessing game project

Add readLine and readInt operations to the Console effect for interactive
input. Create a number guessing game project demonstrating ADTs, pattern
matching, effects, and game state management.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/interpreter.rs

@@ -2880,7 +2880,7 @@ impl Interpreter {
                     Ok(Value::Unit)
                 }
             }
-            ("Console", "read") => {
+            ("Console", "read") | ("Console", "readLine") => {
                 let mut input = String::new();
                 std::io::stdin()
                     .read_line(&mut input)
@@ -2890,6 +2890,23 @@ impl Interpreter {
                     })?;
                 Ok(Value::String(input.trim().to_string()))
             }
+            ("Console", "readInt") => {
+                let mut input = String::new();
+                std::io::stdin()
+                    .read_line(&mut input)
+                    .map_err(|e| RuntimeError {
+                        message: format!("Failed to read input: {}", e),
+                        span: None,
+                    })?;
+                let trimmed = input.trim();
+                match trimmed.parse::<i64>() {
+                    Ok(n) => Ok(Value::Int(n)),
+                    Err(_) => Err(RuntimeError {
+                        message: format!("Invalid integer: '{}'", trimmed),
+                        span: None,
+                    }),
+                }
+            }
             ("Fail", "fail") => {
                 let msg = request
                     .args

src/types.rs

@@ -780,6 +780,16 @@ impl TypeEnv {
                         params: Vec::new(),
                         return_type: Type::String,
                     },
+                    EffectOpDef {
+                        name: "readLine".to_string(),
+                        params: Vec::new(),
+                        return_type: Type::String,
+                    },
+                    EffectOpDef {
+                        name: "readInt".to_string(),
+                        params: Vec::new(),
+                        return_type: Type::Int,
+                    },
                 ],
             },
         );