refactor: Remove PlatformRefs field from LiveState struct

PlatformRefs was a documentation-only field tracking tenant override
sagas. Since tenant overrides are not in SystemCodes, they pass through
filterTenantOwned without any special handling. The field added no
behavioural value and is removed along with the associated test cases.

Author: bjcoombs

services/control-plane/internal/differ/live_state.go

@@ -29,27 +29,18 @@ type LiveState struct {
 	// Outer key is ResourceType, inner key is the resource code/name.
 	// Resources in this set are excluded from diff planning by filterTenantOwned.
 	SystemCodes map[ResourceType]map[string]bool
-
-	// PlatformRefs tracks resources that are tenant overrides of platform defaults
-	// (is_system=false with a non-nil platform_ref in the service layer).
-	// These are tenant-owned resources and must be included in diff planning.
-	// Outer key is ResourceType, inner key is the resource code/name.
-	PlatformRefs map[ResourceType]map[string]bool
 }
 
 // filterTenantOwned returns a copy of live with platform default resources removed.
 // Resources present in SystemCodes (is_system=true) are excluded from all resource slices.
-// Resources present in PlatformRefs (is_system=false with platform_ref) are tenant overrides
-// and are naturally retained - they are not in SystemCodes and pass through unchanged.
 // This function must be called before DiffAgainstLiveState to ensure system resources
 // do not appear as CREATE or UPDATE actions.
 func filterTenantOwned(live *LiveState) *LiveState {
 	if live == nil {
 		return nil
 	}
 	return &LiveState{
-		SystemCodes:  live.SystemCodes,
-		PlatformRefs: live.PlatformRefs,
+		SystemCodes: live.SystemCodes,
 		Instruments: filterBySystemCodes(live.Instruments, live.SystemCodes, ResourceInstrument,
 			func(r *controlplanev1.InstrumentDefinition) string { return r.GetCode() }),
 		AccountTypes: filterBySystemCodes(live.AccountTypes, live.SystemCodes, ResourceAccountType,

services/control-plane/internal/differ/live_state_filter_test.go

@@ -88,37 +88,6 @@ func TestFilterTenantOwned_Sagas_SystemFiltered(t *testing.T) {
 	assert.Equal(t, "tenant_custom_saga", result.Sagas[0].GetName())
 }
 
-// TestFilterTenantOwned_SagaOverride_Retained verifies that a tenant override saga
-// (is_system=false with platform_ref) is retained after filtering.
-// Tenant overrides are not in SystemCodes (they are not platform defaults), so they
-// pass through filterTenantOwned and must be included in diff planning.
-func TestFilterTenantOwned_SagaOverride_Retained(t *testing.T) {
-	live := &LiveState{
-		Sagas: []*controlplanev1.SagaDefinition{
-			// Platform default: is_system=true, filtered out.
-			{Name: "platform_saga"},
-			// Tenant override: is_system=false, has platform_ref (tracked in PlatformRefs).
-			{Name: "override_saga"},
-			// Regular tenant saga: no platform_ref.
-			{Name: "custom_saga"},
-		},
-		SystemCodes: map[ResourceType]map[string]bool{
-			ResourceSaga: {"platform_saga": true},
-		},
-		// PlatformRefs documents which sagas are tenant overrides of platform defaults.
-		PlatformRefs: map[ResourceType]map[string]bool{
-			ResourceSaga: {"override_saga": true},
-		},
-	}
-	result := filterTenantOwned(live)
-	require.NotNil(t, result)
-	require.Len(t, result.Sagas, 2, "both override_saga and custom_saga should be retained")
-	names := sagaNames(result.Sagas)
-	assert.Contains(t, names, "override_saga")
-	assert.Contains(t, names, "custom_saga")
-	assert.NotContains(t, names, "platform_saga")
-}
-
 func TestFilterTenantOwned_MultipleTypes(t *testing.T) {
 	live := &LiveState{
 		Instruments: []*controlplanev1.InstrumentDefinition{
@@ -226,20 +195,15 @@ func TestFilterTenantOwned_AllResourceTypesFiltered(t *testing.T) {
 	assert.Equal(t, "tenant-route", result.InstructionRoutes[0].GetInstructionType())
 }
 
-func TestFilterTenantOwned_PreservesSystemAndPlatformRefMaps(t *testing.T) {
+func TestFilterTenantOwned_PreservesSystemCodesMap(t *testing.T) {
 	systemCodes := map[ResourceType]map[string]bool{
 		ResourceInstrument: {"SYS_GBP": true},
 	}
-	platformRefs := map[ResourceType]map[string]bool{
-		ResourceSaga: {"override_saga": true},
-	}
 	live := &LiveState{
-		SystemCodes:  systemCodes,
-		PlatformRefs: platformRefs,
+		SystemCodes: systemCodes,
 	}
 	result := filterTenantOwned(live)
 	assert.Equal(t, systemCodes, result.SystemCodes)
-	assert.Equal(t, platformRefs, result.PlatformRefs)
 }
 
 // --- helpers ---
@@ -251,11 +215,3 @@ func instrumentCodes(instruments []*controlplanev1.InstrumentDefinition) []strin
 	}
 	return codes
 }
-
-func sagaNames(sagas []*controlplanev1.SagaDefinition) []string {
-	names := make([]string, len(sagas))
-	for i, s := range sagas {
-		names[i] = s.GetName()
-	}
-	return names
-}