Rename mount label to "FixtureKit Insert" and harden coder subscriber

The execute_batch label for fixture mount changes from "FixtureKit Load"
to "FixtureKit Insert" to align with Rails' own fixture insert naming.

The label rename causes fixture_kit's own mount notifications to match
the coder's NAME_PATTERN (which recognizes "Insert" as a write verb).
Without a guard, nested fixture inheritance would feed the parent's
mount notification back into the child's generate subscriber and
constantize "FixtureKit" — the module, not a class — and crash inside
base_table_model.

Switch the subscriber to safe_constantize and require the result to be
a Class < ActiveRecord::Base before capturing it. Non-AR matches are
silently skipped instead of raising.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: ngan

lib/fixture_kit/coders/active_record_coder.rb

@@ -15,7 +15,10 @@ def generate(parent_data: nil, &block)
         model_name = name[NAME_PATTERN, :model_name]
         next unless model_name
 
-        captured_models.add(ActiveSupport::Inflector.constantize(model_name))
+        klass = ActiveSupport::Inflector.safe_constantize(model_name)
+        next unless klass.is_a?(Class) && klass < ActiveRecord::Base
+
+        captured_models.add(klass)
       end
 
       ActiveSupport::Notifications.subscribed(subscriber, EVENT, monotonic: true, &block)
@@ -31,7 +34,7 @@ def mount(data)
         connection.disable_referential_integrity do
           # execute_batch is private in current supported Rails versions.
           # This should be revisited when Rails 8.2 makes it public.
-          connection.__send__(:execute_batch, statements, "FixtureKit Load")
+          connection.__send__(:execute_batch, statements, "FixtureKit Insert")
         end
       end
     end

spec/unit/coders/active_record_coder_spec.rb

@@ -140,9 +140,9 @@ def exercise_user_write_operations(suffix)
       ]
 
       expect(primary_connection).to receive(:disable_referential_integrity).once.and_yield
-      expect(primary_connection).to receive(:execute_batch).with(primary_statements, "FixtureKit Load").once
+      expect(primary_connection).to receive(:execute_batch).with(primary_statements, "FixtureKit Insert").once
       expect(analytics_connection).to receive(:disable_referential_integrity).once.and_yield
-      expect(analytics_connection).to receive(:execute_batch).with(analytics_statements, "FixtureKit Load").once
+      expect(analytics_connection).to receive(:execute_batch).with(analytics_statements, "FixtureKit Insert").once
 
       coder.mount(records)
     end

spec/unit/fixture_cache_spec.rb

@@ -356,9 +356,9 @@ def identifier_for(identifier)
       ]
 
       expect(primary_connection).to receive(:disable_referential_integrity).once.and_yield
-      expect(primary_connection).to receive(:execute_batch).with(primary_statements, "FixtureKit Load").once
+      expect(primary_connection).to receive(:execute_batch).with(primary_statements, "FixtureKit Insert").once
       expect(analytics_connection).to receive(:disable_referential_integrity).once.and_yield
-      expect(analytics_connection).to receive(:execute_batch).with(analytics_statements, "FixtureKit Load").once
+      expect(analytics_connection).to receive(:execute_batch).with(analytics_statements, "FixtureKit Insert").once
 
       expect(cache.load).to eq(:repository)
     end