feat: Initialize compiler GUI project

Sets up the basic structure for the compiler GUI application using
eframe.
This includes the main application loop, a default UI layout with a
source code editor and an output log panel, and the foundational AST
(Abstract Syntax Tree) definitions for types, nodes, and an evaluation
mechanism.

src/ast/types.rs

@@ -0,0 +1,62 @@
+use std::sync::Arc;
+use std::collections::HashMap;
+use std::fmt;
+
+/// Shared identity for nodes (Location, etc.)
+#[derive(Debug, Clone)]
+pub struct NodeIdentity {
+    pub line: u32,
+    pub col: u32,
+}
+
+pub type Identity = Arc<NodeIdentity>;
+
+/// Interned string identifier
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Keyword(pub u32);
+
+/// Core data value in Myc Script (similar to TDataValue)
+#[derive(Clone)]
+pub enum Value {
+    Nil,
+    Bool(bool),
+    Int(i64),
+    Float(f64),
+    Text(Arc<str>),
+    Keyword(Keyword),
+    List(Arc<Vec<Value>>),
+    Record(Arc<HashMap<Keyword, Value>>),
+    Function(Arc<dyn Fn(Vec<Value>) -> Value + Send + Sync>),
+}
+
+impl Value {
+    pub fn is_truthy(&self) -> bool {
+        match self {
+            Value::Nil => false,
+            Value::Bool(b) => *b,
+            _ => true,
+        }
+    }
+}
+
+impl fmt::Display for Value {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Value::Nil => write!(f, "nil"),
+            Value::Bool(b) => write!(f, "{}", b),
+            Value::Int(i) => write!(f, "{}", i),
+            Value::Float(fl) => write!(f, "{}", fl),
+            Value::Text(t) => write!(f, "\"{}\"", t),
+            Value::Keyword(k) => write!(f, ":kw#{}", k.0),
+            Value::List(l) => write!(f, "<list[{}]>", l.len()),
+            Value::Record(r) => write!(f, "<record[{}]>", r.len()),
+            Value::Function(_) => write!(f, "<fn>"),
+        }
+    }
+}
+
+impl fmt::Debug for Value {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(self, f)
+    }
+}