fix: cap forced-retention edits to the message's earlier expiry

The edit/feedback path calls applyForcedRetention with capExpiryToConversation,
which unconditionally set the touched message's expiredAt to the parent/fresh
forced deadline. When that message already expired sooner (an older message
keeps its creation-time deadline while later saves refreshed the parent's), the
$set extended it past its own schedule, overwriting the earlier deadline that
capForcedRetentionToParent had just preserved.

Cap the touched message to min(existing expiredAt, forcedExpiredAt) via the same
$min/$ifNull pipeline forceConversationMessagesTemporary already uses, so a
message with a sooner deadline keeps it and a permanent message still receives
the forced one.

packages/data-schemas/src/methods/message.spec.ts

@@ -1128,6 +1128,42 @@ describe('Message Operations', () => {
       }
     });
 
+    it('preserves an edited message expiring sooner than its parent under forced retention', async () => {
+      const conversationId = uuidv4();
+      const editedMessageId = uuidv4();
+      const messageDeadline = new Date(Date.now() + 60 * 60 * 1000);
+      const parentDeadline = new Date(Date.now() + 12 * 60 * 60 * 1000);
+      await Conversation().create({
+        conversationId,
+        user: 'user123',
+        endpoint: 'openAI',
+        title: 'Carried-over chat',
+        isTemporary: false,
+        expiredAt: parentDeadline,
+      });
+      await Message.create({
+        messageId: editedMessageId,
+        conversationId,
+        user: 'user123',
+        text: 'edited',
+        isTemporary: false,
+        expiredAt: messageDeadline,
+      });
+
+      await applyForcedRetention(
+        {
+          userId: 'user123',
+          interfaceConfig: { temporaryChatRetention: 24, retentionMode: RetentionMode.EPHEMERAL },
+        },
+        { conversationId, messageId: editedMessageId },
+        { context: 'edit', capExpiryToConversation: true },
+      );
+
+      const message = await Message.findOne({ messageId: editedMessageId, user: 'user123' }).lean();
+      expect(message?.isTemporary).toBe(true);
+      expect(message?.expiredAt?.getTime()).toBe(messageDeadline.getTime());
+    });
+
     it('converts a permanent conversation and its messages without a messageId (tag write)', async () => {
       const conversationId = uuidv4();
       await Conversation().create({

packages/data-schemas/src/methods/message.ts

@@ -422,10 +422,14 @@ export function createMessageMethods(mongoose: typeof import('mongoose')): Messa
     }
 
     if (typeof messageId === 'string' && messageId.length > 0) {
-      await Message.updateOne(
-        { messageId, user: userId },
-        { $set: { isTemporary: true, expiredAt: forcedExpiredAt } },
-      );
+      await Message.updateOne({ messageId, user: userId }, [
+        {
+          $set: {
+            isTemporary: true,
+            expiredAt: { $min: [{ $ifNull: ['$expiredAt', forcedExpiredAt] }, forcedExpiredAt] },
+          },
+        },
+      ]);
     }
     await cascadeForcedConversationRetention(
       Conversation,