Add statement parsing with error recovery

- ast.rs: add Type, Block, ElseBranch, Stmt, StmtKind
- parser.rs: parse_type, parse_block, parse_stmt and all sub-parsers;
  missing-token insertion via expect(), synchronize() for panic-mode
  recovery on non-startable tokens; 26 new tests (62 total)
- main.rs: REPL now parses statements instead of bare expressions

fluxc/src/ast.rs

@@ -35,6 +35,38 @@ pub enum BinaryOp {
     Rem, // `%`
 }
 
+// ── Types ──────────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone)]
+pub enum Type {
+    // Unsigned integers
+    U8,
+    U16,
+    U32,
+    U64,
+    // Signed integers
+    I8,
+    I16,
+    I32,
+    I64,
+    // Floating-point
+    F32,
+    F64,
+    // Other primitives
+    Bool,
+    Char,
+    // User-defined named type (e.g. a struct)
+    Named(String, Span),
+    // Typed pointer: `*type`
+    Pointer(Box<Type>),
+    // Opaque (untyped) pointer: `*opaque`
+    OpaquePointer,
+    // Fixed-size array: `[type; INT_LIT]`
+    Array { elem: Box<Type>, size: String },
+    // Error placeholder for recovery
+    Error,
+}
+
 // ── Struct literal field ───────────────────────────────────────────────────────
 
 #[derive(Debug, Clone)]
@@ -111,3 +143,61 @@ pub enum ExprKind {
     // Placeholder for parse errors — allows parsing to continue
     Error,
 }
+
+// ── Block ──────────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone)]
+pub struct Block {
+    pub stmts: Vec<Stmt>,
+    pub span: Span,
+}
+
+// ── Else branch ───────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone)]
+pub enum ElseBranch {
+    If(Box<Stmt>), // `else if …`
+    Block(Block),  // `else { … }`
+}
+
+// ── Statement ─────────────────────────────────────────────────────────────────
+
+#[derive(Debug, Clone)]
+pub struct Stmt {
+    pub kind: StmtKind,
+    pub span: Span,
+}
+
+#[derive(Debug, Clone)]
+pub enum StmtKind {
+    /// `let [mut] name [: type] [= expr] ;`
+    Let {
+        mutable: bool,
+        name: String,
+        name_span: Span,
+        ty: Option<Type>,
+        init: Option<Expr>,
+    },
+    /// `return [expr] ;`
+    Return(Option<Expr>),
+    /// `if expr_ns block [else else_branch]`
+    If {
+        cond: Expr,
+        then_block: Block,
+        else_branch: Option<ElseBranch>,
+    },
+    /// `while expr_ns block`
+    While { cond: Expr, body: Block },
+    /// `loop block`
+    Loop { body: Block },
+    /// `break ;`
+    Break,
+    /// `continue ;`
+    Continue,
+    /// `{ stmts }`
+    Block(Block),
+    /// `expr ;`
+    Expr(Expr),
+    /// Error placeholder — emitted during recovery so the parent can continue.
+    Error,
+}