fix(config): an ordinary save without led_strips keeps the stored shapes (#780)

r1 H1: a previous frontend sends every space without the unknown field and
the ordinary write path replaced the document with it, erasing every LED
strip. The shared ordinary-writer helper now copies the stored shapes of a
space the payload omits (config/set and Optimize); an explicit list from a
new client still deletes, a removed space takes its strips, and a link to a
marker the same write deleted unbinds by the usual rule. config/set reports
the normalisation counters after the preservation.

Issue: #780
User-Visible: no

scripts/mutation-registry.mjs

@@ -14374,6 +14374,16 @@ const MUTANT_DEFINITIONS = [
       replace: '    unbound_led_strips = unbind_strips(space, remap={\n        old_id: old_id for old_id, new_id in marker_map.items()',
     }],
   },
+  {
+    id: 'led-old-writer-drops-strips',
+    guard: 'node scripts/backend-test-guard.mjs old_writer tests_backend/test_led_strips.py',
+    because: '#780 r1 H1: an ordinary save without the unknown field keeps the stored shapes; only an explicit list deletes',
+    patches: [{
+      file: 'custom_components/houseplan/validation.py',
+      find: '    preserve_summary_panel_namespace(candidate, previous)\n    preserve_led_strips(candidate, previous)',
+      replace: '    preserve_summary_panel_namespace(candidate, previous)',
+    }],
+  },
 ];
 
 const mutationCardSource = readFileSync(join(repoRoot, 'src/houseplan-card.ts'), 'utf8');