Don't report starved thermals when connected only to isolated islands.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/16866

pcbnew/drc/drc_test_provider_zone_connections.cpp

@@ -196,6 +196,18 @@ void DRC_TEST_PROVIDER_ZONE_CONNECTIONS::testZoneLayer( ZONE* aZone, PCB_LAYER_I
                 }
             }
 
+            //
+            // If we're *only* connected to isolated islands, then ignore the fact that they're
+            // isolated.  (We leave that for the connectivity tester, which checks connections on
+            // all layers.)
+            //
+
+            if( spokes == 0 )
+            {
+                spokes += ignoredSpokes;
+                ignoredSpokes = 0;
+            }
+
             //
             // And finally report it if there aren't enough:
             //

qa/tests/pcbnew/drc/test_drc_regressions.cpp

@@ -123,10 +123,10 @@ BOOST_FIXTURE_TEST_CASE( DRCFalseNegativeRegressions, DRC_REGRESSION_TEST_FIXTUR
 
     std::vector< std::pair<wxString, int> > tests =
     {
-        { "issue1358",  3 },
+        { "issue1358",  2 },
         { "issue2512",  5 },
         { "issue2528",  1 },
-        { "issue5750",  6 },   // Shorting zone fills pass DRC in some cases
+        { "issue5750",  4 },   // Shorting zone fills pass DRC in some cases
         { "issue5854",  3 },
         { "issue6879",  6 },
         { "issue6945",  2 },
@@ -139,7 +139,7 @@ BOOST_FIXTURE_TEST_CASE( DRCFalseNegativeRegressions, DRC_REGRESSION_TEST_FIXTUR
         { "issue14334", 2 },        // Thermal spoke to otherwise unconnected island
         { "issue16566", 6 },        // Pad_Shape vs Shape property
         { "reverse_via", 3 },       // Via/track ordering
-        { "intersectingzones", 2 }, // zones are too close to each other
+        { "intersectingzones", 1 }, // zones are too close to each other
         { "fill_bad",   1 }         // zone max BBox was too small
     };