Add email thread widget and message thread record page layout (#19351)

## Summary
- Move email thread display from side panel to a dedicated record page
with a new `EMAIL_THREAD` widget type
- Add message thread as a standard object with page layout, subject
field, and backfill command
- Add reply-to-email command menu item for message thread records
- Remove old side panel message thread components in favor of the new
widget-based approach

## Type fixes
- Add `EMAIL_THREAD` to `WidgetConfigurationType`, `WidgetType`, and all
configuration/validator maps
- Create `EmailThreadConfigurationDTO` and shared
`EmailThreadConfiguration` type
- Register EMAIL_THREAD in widget type validators, configuration
resolvers, and standard widget mappings

## Test plan
- [ ] Verify message thread record pages render with the email thread
widget
- [ ] Verify email thread preview navigates to the record page instead
of opening side panel
- [ ] Verify reply-to-email command appears for message thread records
- [ ] Verify typecheck passes for both twenty-front and twenty-server
- [ ] Run existing test suites to check for regressions

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/twenty-front/src/modules/command-menu-item/engine-command/constants/EngineComponentKeyHeadlessComponentMap.tsx

@@ -40,6 +40,7 @@ import { TestWorkflowSingleRecordCommand } from '@/command-menu-item/engine-comm
 import { TidyUpWorkflowSingleRecordCommand } from '@/command-menu-item/engine-command/record/single-record/workflow/components/TidyUpWorkflowSingleRecordCommand';
 import { HeadlessFrontComponentRendererEngineCommand } from '@/command-menu-item/engine-command/components/HeadlessFrontComponentRendererEngineCommand';
 import { TriggerWorkflowVersionEngineCommand } from '@/command-menu-item/engine-command/record/components/TriggerWorkflowVersionEngineCommand';
+import { ReplyToEmailThreadCommand } from '@/command-menu-item/engine-command/record/single-record/message-thread/components/ReplyToEmailThreadCommand';
 import { CoreObjectNamePlural } from '@/object-metadata/types/CoreObjectNamePlural';
 import { msg } from '@lingui/core/macro';
 import { AppPath, SettingsPath, SidePanelPages } from 'twenty-shared/types';
@@ -240,6 +241,7 @@ export const ENGINE_COMPONENT_KEY_COMPONENT_MAP: Record<
   [EngineComponentKey.FRONT_COMPONENT_RENDERER]: (
     <HeadlessFrontComponentRendererEngineCommand />
   ),
+  [EngineComponentKey.REPLY_TO_EMAIL_THREAD]: <ReplyToEmailThreadCommand />,
 
   // Deprecated keys kept for backward compatibility until migration runs
   [EngineComponentKey.DELETE_SINGLE_RECORD]: <DeleteRecordsCommand />,

packages/twenty-front/src/modules/command-menu-item/engine-command/record/single-record/message-thread/components/ReplyToEmailThreadCommand.tsx

@@ -0,0 +1,78 @@
+import { useMemo } from 'react';
+
+import { useEmailThread } from '@/activities/emails/hooks/useEmailThread';
+import { HeadlessEngineCommandWrapperEffect } from '@/command-menu-item/engine-command/components/HeadlessEngineCommandWrapperEffect';
+import { useHeadlessCommandContextApi } from '@/command-menu-item/engine-command/hooks/useHeadlessCommandContextApi';
+import { ConnectedAccountProvider } from 'twenty-shared/types';
+import { isDefined } from 'twenty-shared/utils';
+
+const ALLOWED_REPLY_PROVIDERS = [
+  ConnectedAccountProvider.GOOGLE,
+  ConnectedAccountProvider.MICROSOFT,
+  ConnectedAccountProvider.IMAP_SMTP_CALDAV,
+];
+
+export const ReplyToEmailThreadCommand = () => {
+  const { selectedRecords } = useHeadlessCommandContextApi();
+  const threadId = selectedRecords[0]?.id ?? null;
+
+  const {
+    messageThreadExternalId,
+    connectedAccountHandle,
+    connectedAccountProvider,
+    lastMessageExternalId,
+    connectedAccountConnectionParameters,
+    messageChannelLoading,
+  } = useEmailThread(threadId);
+
+  const canReply = useMemo(() => {
+    return (
+      isDefined(connectedAccountHandle) &&
+      isDefined(connectedAccountProvider) &&
+      ALLOWED_REPLY_PROVIDERS.includes(connectedAccountProvider) &&
+      (connectedAccountProvider !== ConnectedAccountProvider.IMAP_SMTP_CALDAV ||
+        isDefined(connectedAccountConnectionParameters?.SMTP)) &&
+      isDefined(messageThreadExternalId)
+    );
+  }, [
+    connectedAccountConnectionParameters,
+    connectedAccountHandle,
+    connectedAccountProvider,
+    messageThreadExternalId,
+  ]);
+
+  const handleExecute = () => {
+    if (!canReply) {
+      return;
+    }
+
+    switch (connectedAccountProvider) {
+      case ConnectedAccountProvider.MICROSOFT: {
+        const url = `https://outlook.office.com/mail/deeplink?ItemID=${lastMessageExternalId}`;
+        window.open(url, '_blank');
+        break;
+      }
+      case ConnectedAccountProvider.GOOGLE: {
+        const url = `https://mail.google.com/mail/?authuser=${connectedAccountHandle}#all/${messageThreadExternalId}`;
+        window.open(url, '_blank');
+        break;
+      }
+      case ConnectedAccountProvider.IMAP_SMTP_CALDAV:
+      case ConnectedAccountProvider.OIDC:
+      case ConnectedAccountProvider.SAML:
+      case null:
+        return;
+      default:
+        return;
+    }
+  };
+
+  const isReady = !messageChannelLoading && canReply;
+
+  return (
+    <HeadlessEngineCommandWrapperEffect
+      execute={handleExecute}
+      ready={isReady}
+    />
+  );
+};