Implement Misses DSL compiler (parser + codegen)

- ast.rs: Full AST for .mrs files (MacroDef, Pattern, OutputBody, TemplateItem)
- parser.rs: Hand-written recursive descent parser with line/col error reporting
- codegen.rs: Transforms AST to Rust proc macro code using syn/quote/proc_macro2
- main.rs: CLI reads .mrs file, runs parse→codegen, writes to stdout or file
- Cargo.toml: Workspace with syn, quote, proc-macro2, prettyplease deps
- examples/: hello.mrs, derive_builder.mrs, declare_table.mrs reference examples

All three reference examples parse and produce prettyplease-formatted Rust output.
Generated code uses syn::parse::Parser closures for structural patterns, quote!
for token templates, spread iteration via .iter().map().collect(), and
format_ident! for identifier construction.

https://claude.ai/code/session_01Tppkab4eLsL21asHGjQJoF

examples/derive_builder.mrs

@@ -0,0 +1,21 @@
+macro derive_builder! {
+    struct $name:ident { $($field:ident : $ty:ty),* } => {
+        @{
+            let builder_name = format_ident!("{}_Builder", name.to_string());
+        }
+        T~{
+            pub struct ${ builder_name } {
+                for field in $fields =>
+                    pub $field.name: Option<$field.ty>,
+            }
+            impl ${ builder_name } {
+                pub fn build(self) -> $name {
+                    $name {
+                        for field in $fields =>
+                            $field.name: self.$field.name.unwrap(),
+                    }
+                }
+            }
+        }
+    }
+}