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/examples/derive_getters.mrs

@@ -0,0 +1,13 @@
+// derive_getters.mrs — auto-generate getter methods
+// Demonstrates: struct pattern, variadic binding, spread iteration generating
+//               impl methods with reference return types
+macro derive_getters! {
+    struct $name:ident { $($field:ident : $ty:ty),* } => {
+        T~{
+            impl $name {
+                for field in $fields =>
+                    pub fn $field.name(&self) -> &$field.ty { &self.$field.name }
+            }
+        }
+    }
+}