feat: discovery filters become visible, explained and previewable (#44)

Light grouping and the excluded-integrations list move from hidden keys
to a Discovery-filters section on the catalog's Available tab: a toggle
(unset = on, the legacy behaviour), searchable integration chips with a
Restore-recommended reset (defaults stored as key absence), and
appear/disappear counters computed by diffing the REAL
seedHiddenBindings/buildDevices outputs — no second copy of the filter.
Saving writes settings once over the ordinary expected_rev path. Every
excluded candidate now names its integration in the catalog. Room
climate follows the same user exclusions through the single
effectiveExcludedIntegrations resolver (spec H2); explicit climate
opt-in stays stronger. The field registry passports both keys as
current supported settings.

User-Visible: yes
Issue: #44

scripts/config-field-registry.mjs

@@ -44,14 +44,15 @@ export const CONFIG_FIELD_REGISTRY = Object.freeze([
     selector: { path: ['settings', 'group_lights'] },
     storage: 'House Plan server config',
     type: 'boolean',
-    default: 'unset',
+    default: 'unset (= true: room lights grouped)',
     level: 'global',
-    ui: 'hidden',
+    ui: 'device inbox → Discovery filters (#44)',
     runtime: 'device discovery/materialisation',
-    introduced: 'legacy',
-    status: 'decision-required',
-    migration: 'decide supported UI versus fixed discovery rule before removal',
-    compatibility: 'preserve unknown owner intent; never delete automatically yet',
+    introduced: 'legacy; supported UI since #44',
+    status: 'current',
+    migration: 'none — a supported setting; true is stored as key absence',
+    compatibility: 'unset keeps grouping on, exactly the legacy behaviour',
+    enforcedBy: 'demo/smoke_discovery_filters.mjs (#44 AC1)',
   },
   {
     id: 'settings.exclude_integrations',
@@ -59,14 +60,15 @@ export const CONFIG_FIELD_REGISTRY = Object.freeze([
     selector: { path: ['settings', 'exclude_integrations'] },
     storage: 'House Plan server config',
     type: 'string[]',
-    default: 'unset',
+    default: 'unset (= the product EXCLUDED_DOMAINS list)',
     level: 'global',
-    ui: 'hidden',
-    runtime: 'device discovery filter',
-    introduced: 'legacy',
-    status: 'decision-required',
-    migration: 'decide supported UI versus fixed exclusion rules before removal',
-    compatibility: 'preserve and continue applying',
+    ui: 'device inbox → Discovery filters (#44)',
+    runtime: 'device discovery, materialisation seed, room climate (#44 H2) — one resolver',
+    introduced: 'legacy; supported UI since #44',
+    status: 'current',
+    migration: 'none — a supported setting; a present list REPLACES the product list wholesale',
+    compatibility: 'unset keeps the product list; [] is a valid "exclude nothing"',
+    enforcedBy: 'effectiveExcludedIntegrations (devices.ts) + demo/smoke_discovery_filters.mjs (#44 AC2)',
   },
   {
     id: 'settings.weather_entity',

scripts/mutation-gate.mjs

@@ -735,6 +735,28 @@ const MUTANT_DEFINITIONS = [
       replace: "      this._persistDecorStyle();\n    }, 0);",
     }],
   },
+  {
+    id: 'discovery-preview-copies-the-filter',
+    guard: 'node --test test/devices.test.mjs',
+    because: 'the preview must diff the REAL seedHiddenBindings/buildDevices outputs — a '
+      + 'hand-rolled platform check would drift from the production filter (#44 AC6)',
+    patches: [{
+      file: 'src/houseplan-editor-runtime.ts',
+      find: "    const seededOf = (settings: object, excluded: ReadonlySet<string>) => new Set(\n      seedHiddenBindings({ ...ctx, settings, excluded } as never));",
+      replace: "    const seededOf = (settings: object, excluded: ReadonlySet<string>) => new Set(\n      [...excluded].filter((platform) => platform && EXCLUDED_DOMAINS.has(platform)));",
+    }],
+  },
+  {
+    id: 'discovery-reset-writes-a-copy',
+    guard: 'node demo/smoke_discovery_filters.mjs',
+    because: 'Restore recommended must store the default as ABSENCE of the key — a written '
+      + 'copy of the product list would freeze it against future product updates (#44 AC2)',
+    patches: [{
+      file: 'src/houseplan-editor-runtime.ts',
+      find: "    if (draft.usesProductList) delete settings.exclude_integrations;\n    else settings.exclude_integrations = draft.excluded;",
+      replace: "    settings.exclude_integrations = draft.excluded;",
+    }],
+  },
   {
     id: 'schema-manifest-enum-drift',
     guard: 'node --test test/config-schema-parity.test.mjs',