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/declare_table.mrs

@@ -0,0 +1,18 @@
+// declare_table.mrs — DSL-to-struct mapping
+// Demonstrates: $body:tt raw token capture, escape block calling misses_rt,
+//               expression injection of a &str
+macro declare_table! {
+    $name:ident { $body:tt } => {
+        @{
+            let table_str = misses_rt::to_table_name(&name);
+        }
+        T~{
+            pub struct $name {
+                pub id: u64,
+            }
+            impl $name {
+                pub const TABLE: &'static str = ${ table_str.as_str() };
+            }
+        }
+    }
+}