Close the two real Codecov patch-coverage gaps from this PR

DeleteWhereImplementer.isCompatibleReturnType and
AbstractServiceImplementer.isValidParameter each had one branch missing
on lines Codecov flagged. Added a compile-error test for a @where delete
method with an incompatible (non-void, non-Number) return type, and a
save-with-id-named-parameter test that exercises isValidParameter's
GormProperties.IDENTITY branch directly (SaveImplementer, unlike
UpdateOneImplementer, doesn't strip the id parameter before validating
it). Both branches now fully covered.

The third flagged line, FindAllByImplementer's matchSpec == null error
path, was verified empirically rather than assumed unreachable: a probe
test with an edge-case DSL input (findAllBy() with no property suffix)
showed doesImplement() already computes the identical memoized matchSpec
before selecting this implementer, so doImplement() can never observe a
null matchSpec -- the method falls through to FindAllImplementer instead
whenever matchSpec would be null. Genuinely unreachable through the
public DSL, not a gap.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: borinquenkid

grails-datamapping-core/src/test/groovy/grails/gorm/services/ServiceImplementerEdgeCaseSpec.groovy

@@ -361,4 +361,53 @@ class Foo {
         then:
         impl.getMethod('saveFoo', String).getAnnotation(grails.gorm.transactions.Transactional) != null
     }
+
+    void 'a @Where delete method with an incompatible return type fails to compile'() {
+        when:
+        new GroovyClassLoader().parseClass('''
+import grails.gorm.services.Service
+import grails.gorm.services.Where
+import grails.gorm.annotation.Entity
+
+@Service(Foo)
+interface FooService {
+    @Where({ title ==~ pattern })
+    String deleteByTitle(String pattern)
+}
+@Entity
+class Foo {
+    String title
+}
+''')
+
+        then:
+        MultipleCompilationErrorsException e = thrown(MultipleCompilationErrorsException)
+        e.message.contains('No implementations possible')
+    }
+
+    void 'a save method with an id-named parameter binds it directly onto the entity'() {
+        when:
+        Class service = new GroovyClassLoader().parseClass('''
+import grails.gorm.services.Service
+import grails.gorm.annotation.Entity
+
+@Service(Foo)
+interface FooService {
+    Foo save(Serializable id, String title)
+}
+@Entity
+class Foo {
+    String title
+}
+''')
+
+        then:
+        service.isInterface()
+
+        when:
+        Class impl = service.classLoader.loadClass("\$FooServiceImplementation")
+
+        then:
+        impl.getMethod('save', Serializable, String).getAnnotation(Implemented).by() == org.grails.datastore.gorm.services.implementers.SaveImplementer
+    }
 }