feat: migrate objectMetadata reads to granular metadata store (#18643)

## Summary

Consolidates `objectMetadataItems` onto the metadata store as the
**single source of truth**, replacing the previous dual-store approach
(separate `objectMetadataItemsState` atom + untyped
`metadataStoreState`).

### Architecture: three-layer design

```
┌─────────────────────────────────────────────────────────┐
│ Store Layer (granular, typed)                           │
│  objectMetadataItems → FlatObjectMetadataItem[]         │
│  fieldMetadataItems  → FlatFieldMetadataItem[]          │
│  indexMetadataItems  → FlatIndexMetadataItem[]           │
└────────────────┬────────────────────────────────────────┘
                 │ .current (never draft)
┌────────────────▼────────────────────────────────────────┐
│ Selectors (typed read-only)                             │
│  objectMetadataItemsSelector                            │
│  fieldMetadataItemsSelector                             │
│  indexMetadataItemsSelector                             │
│  metadataStoreStatusFamilySelector                      │
│  isSystemObjectByNameSingularFamilySelector (narrow)    │
│  activeObjectNameSingularsSelector (narrow)             │
└────────────────┬────────────────────────────────────────┘
                 │ joins objects + fields + indexes + permissions
┌────────────────▼────────────────────────────────────────┐
│ Joining Selector                                        │
│  objectMetadataItemsWithFieldsSelector                  │
│  → produces full ObjectMetadataItem[] with              │
│    readableFields / updatableFields from permissions    │
│  → 12 existing selectors repointed here                 │
└─────────────────────────────────────────────────────────┘
```

### Key changes

- **Granular flat types** (`FlatObjectMetadataItem`,
`FlatFieldMetadataItem`, `FlatIndexMetadataItem`) — objects stored
without embedded fields/indexes, matching backend "Flat" naming
convention
- **Typed write API** — `updateDraft` is now generic via
`MetadataEntityTypeMap`, giving compile-time safety on what data shape
goes to each key
- **Write path refactored** — fetch → split into flat entities via
`splitObjectMetadataItemWithRelated` → write to metadata store directly.
No more dual-write through `objectMetadataItemsState`. Permissions
enrichment moved from write path into the joining selector.
- **SSE effects write directly** — `ObjectMetadataItemSSEEffect` and
`FieldMetadataSSEEffect` now patch the store from the SSE event payload
(create/update/delete) instead of triggering a full re-fetch
- **`objectMetadataItemsState` bridge** — converted from writable
`createAtomState` to read-only `createAtomSelector` that delegates to
the joining selector. All 100+ existing consumers continue to work
without code changes.
- **All selectors use Twenty state API** — `createAtomSelector` /
`createAtomFamilySelector` throughout, no raw `atom()`
- **Narrow selectors** for hot paths —
`isSystemObjectByNameSingularFamilySelector` and
`activeObjectNameSingularsSelector` read from flat objects only,
avoiding re-renders when fields/indexes/permissions change. Placed in
`object-metadata/states/` as higher-level business selectors.
- **Test helper** — `setTestObjectMetadataItemsInMetadataStore` for
tests that need to set up composite object metadata through the store
(clearly named as a testing utility)

### Naming conventions

- `ObjectMetadataItemWithRelated` — type for objects with embedded
fields/indexes (input to split utility)
- `FlatObjectMetadataItem` / `FlatFieldMetadataItem` /
`FlatIndexMetadataItem` — granular store types
- Selector names don't expose "Current" — that's an internal detail of
the metadata store API

### Future work

- Optimistic update API (`updateCurrentOptimistically` with rollback)
- Migrate remaining entities (views, pageLayouts, etc.) to the same
pattern
- Gradually remove `objectMetadataItemsState` bridge once all direct
imports are replaced

## Test plan

- [x] `npx nx typecheck twenty-front` passes
- [x] `npx nx lint:diff-with-main twenty-front` passes
- [ ] Verify app loads correctly with metadata from the store
- [ ] Verify SSE updates (object/field changes) propagate correctly
- [ ] Run existing test suites to confirm no regressions

packages/twenty-front/src/modules/views/hooks/__tests__/useInitializeFilterOnFieldMetadataItemFromViewBarFilterDropdown.test.tsx

@@ -6,7 +6,6 @@ import { objectFilterDropdownFilterIsSelectedComponentState } from '@/object-rec
 import { selectedOperandInDropdownComponentState } from '@/object-record/object-filter-dropdown/states/selectedOperandInDropdownComponentState';
 import { useInitializeFilterOnFieldMetadataItemFromViewBarFilterDropdown } from '@/views/hooks/useInitializeFilterOnFieldMetadataItemFromViewBarFilterDropdown';
 
-import { objectMetadataItemsState } from '@/object-metadata/states/objectMetadataItemsState';
 import {
   jotaiStore,
   resetJotaiStore,
@@ -26,6 +25,7 @@ import { ViewBarFilterDropdownIds } from '@/views/constants/ViewBarFilterDropdow
 import { getFilterTypeFromFieldType } from 'twenty-shared/utils';
 import { generatedMockObjectMetadataItems } from '~/testing/utils/generatedMockObjectMetadataItems';
 import { getMockObjectMetadataItemOrThrow } from '~/testing/utils/getMockObjectMetadataItemOrThrow';
+import { setTestObjectMetadataItemsInMetadataStore } from '~/testing/utils/setTestObjectMetadataItemsInMetadataStore';
 
 const mockPushFocusItemToFocusStack = jest.fn();
 
@@ -46,8 +46,8 @@ const personCreatedAtFieldMetadataItemMock =
   );
 
 const wrapper = ({ children }: { children: React.ReactNode }) => {
-  jotaiStore.set(
-    objectMetadataItemsState.atom,
+  setTestObjectMetadataItemsInMetadataStore(
+    jotaiStore,
     generatedMockObjectMetadataItems,
   );
   return (

packages/twenty-front/src/modules/views/view-picker/hooks/__tests__/useGetAvailableFieldsForCalendar.test.tsx

@@ -1,5 +1,5 @@
-import { objectMetadataItemsState } from '@/object-metadata/states/objectMetadataItemsState';
 import { jotaiStore } from '@/ui/utilities/state/jotai/jotaiStore';
+import { setTestObjectMetadataItemsInMetadataStore } from '~/testing/utils/setTestObjectMetadataItemsInMetadataStore';
 import { ViewComponentInstanceContext } from '@/views/states/contexts/ViewComponentInstanceContext';
 import { viewObjectMetadataIdComponentState } from '@/views/states/viewObjectMetadataIdComponentState';
 import { useGetAvailableFieldsForCalendar } from '@/views/view-picker/hooks/useGetAvailableFieldsForCalendar';
@@ -22,7 +22,7 @@ const createMockObjectMetadataItem = (fields: any[]) => ({
 
 const createWrapper = (objectMetadataItems: any[]) => {
   return ({ children }: { children: ReactNode }) => {
-    jotaiStore.set(objectMetadataItemsState.atom, objectMetadataItems);
+    setTestObjectMetadataItemsInMetadataStore(jotaiStore, objectMetadataItems);
     jotaiStore.set(
       viewObjectMetadataIdComponentState.atomFamily({
         instanceId: mockViewInstanceId,
@@ -80,7 +80,7 @@ describe('useGetAvailableFieldsForCalendar', () => {
     });
 
     expect(result.current.availableFieldsForCalendar).toHaveLength(2);
-    expect(result.current.availableFieldsForCalendar).toEqual([
+    expect(result.current.availableFieldsForCalendar).toMatchObject([
       {
         id: '1',
         type: FieldMetadataType.DATE,

packages/twenty-front/src/modules/views/view-picker/hooks/__tests__/useGetAvailableFieldsToGroupRecordsBy.test.tsx

@@ -1,5 +1,5 @@
-import { objectMetadataItemsState } from '@/object-metadata/states/objectMetadataItemsState';
 import { jotaiStore } from '@/ui/utilities/state/jotai/jotaiStore';
+import { setTestObjectMetadataItemsInMetadataStore } from '~/testing/utils/setTestObjectMetadataItemsInMetadataStore';
 import { ViewComponentInstanceContext } from '@/views/states/contexts/ViewComponentInstanceContext';
 import { viewObjectMetadataIdComponentState } from '@/views/states/viewObjectMetadataIdComponentState';
 import { useGetAvailableFieldsToGroupRecordsBy } from '@/views/view-picker/hooks/useGetAvailableFieldsToGroupRecordsBy';
@@ -22,7 +22,7 @@ const createMockObjectMetadataItem = (fields: any[]) => ({
 
 const createWrapper = (objectMetadataItems: any[]) => {
   return ({ children }: { children: ReactNode }) => {
-    jotaiStore.set(objectMetadataItemsState.atom, objectMetadataItems);
+    setTestObjectMetadataItemsInMetadataStore(jotaiStore, objectMetadataItems);
     jotaiStore.set(
       viewObjectMetadataIdComponentState.atomFamily({
         instanceId: mockViewInstanceId,