Add examples with cargo run --example support

- Move .mrs files into misses-compiler/examples/ alongside .rs runners
- Add lib.rs exposing parse/codegen for use by example binaries and main.rs
- Fix parser: #[attr] vs #[a => b] disambiguation (look for => before ])
- Fix parser: `for` keyword in `impl Foo for Bar` no longer triggers spread
  (is_spread_for lookahead: must match `for <ident> in $<ident> =>`)
- Add derive_getters.mrs: getter methods via spread iteration
- Add make_id_type.mrs: newtype u64 wrapper with From impls, derive attrs

Run with: cargo run --example hello|derive_builder|declare_table|derive_getters|make_id_type

https://claude.ai/code/session_01Tppkab4eLsL21asHGjQJoF

misses-compiler/src/main.rs

@@ -1,7 +1,3 @@
-mod ast;
-mod parser;
-mod codegen;
-
 use std::path::PathBuf;
 
 fn main() {
@@ -20,7 +16,7 @@ fn main() {
         }
     };
 
-    let ast = match parser::parse(&src) {
+    let ast = match misses::parse(&src) {
         Ok(a) => a,
         Err(e) => {
             eprintln!("Parse error: {}", e);
@@ -28,7 +24,7 @@ fn main() {
         }
     };
 
-    let generated = codegen::codegen(&ast);
+    let generated = misses::codegen(&ast);
 
     if args.len() >= 3 {
         let output_path = PathBuf::from(&args[2]);