CLDC-4188: Infer referral_register for renewals

needs a new dependencies array for 2026

this handles inferring as well as clearing inferred answers if the prior answer changes

app/models/derived_variables/lettings_log_variables.rb

@@ -33,7 +33,7 @@ module DerivedVariables::LettingsLogVariables
 
   def set_derived_fields!
     clear_inapplicable_derived_values!
-    set_encoded_derived_values!(DEPENDENCIES)
+    set_encoded_derived_values!(dependencies)
 
     if rsnvac.present?
       self.newprop = has_first_let_vacancy_reason? ? 1 : 2
@@ -177,7 +177,54 @@ module DerivedVariables::LettingsLogVariables
 
 private
 
-  DEPENDENCIES = [
+  def dependencies
+    if form.start_year_2026_or_later?
+      DEPENDENCIES_2026
+    else
+      DEPENDENCIES_PRE_2026
+    end
+  end
+
+  DEPENDENCIES_2026 = [
+    {
+      conditions: {
+        renewal: 1,
+      },
+      derived_values: {
+        referral_register: 1, # new in 2026
+        waityear: 2,
+        offered: 0,
+        rsnvac: 14,
+        first_time_property_let_as_social_housing: 0,
+      },
+    },
+    {
+      conditions: {
+        net_income_known: 2,
+      },
+      derived_values: {
+        incref: 1,
+      },
+    },
+    {
+      conditions: {
+        net_income_known: 0,
+      },
+      derived_values: {
+        incref: 0,
+      },
+    },
+    {
+      conditions: {
+        net_income_known: 1,
+      },
+      derived_values: {
+        incref: 2,
+      },
+    },
+  ].freeze
+
+  DEPENDENCIES_PRE_2026 = [
     {
       conditions: {
         renewal: 1,
@@ -218,7 +265,7 @@ private
   ].freeze
 
   def clear_inapplicable_derived_values!
-    reset_invalidated_derived_values!(DEPENDENCIES)
+    reset_invalidated_derived_values!(dependencies)
     if (startdate_changed? || renewal_changed?) && (renewal_was == 1 && startdate_was&.between?(Time.zone.local(2021, 4, 1), Time.zone.local(2022, 3, 31)))
       self.underoccupation_benefitcap = nil
     end

app/models/form/lettings/pages/referral_register_la.rb

@@ -10,6 +10,6 @@ class Form::Lettings::Pages::ReferralRegisterLa < ::Form::Page
   end
 
   def routed_to?(log, _current_user)
-    log.owning_organisation&.la?
+    log.owning_organisation&.la? && !log.is_renewal?
   end
 end

app/models/form/lettings/questions/referral_register.rb

@@ -38,5 +38,9 @@ class Form::Lettings::Questions::ReferralRegister < ::Form::Question
     end
   end
 
+  def derived?(log)
+    log.is_renewal?
+  end
+
   QUESTION_NUMBER_FROM_YEAR = { 2026 => 84 }.freeze
 end