fix(copilot): thread chatModel through post + terminal-state dual-writes

The user-message append path (post.ts) and assistant-finalize path
(terminal-state.ts) were calling appendCopilotChatMessages without
chatModel, leaving the model column NULL on every interactive turn.
post.ts now projects model from .returning(...); terminal-state.ts
adds model to the in-tx SELECT and surfaces it through a closure.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: waleedlatif1

apps/sim/lib/copilot/chat/post.ts

@@ -331,10 +331,13 @@ async function persistUserMessage(params: {
           updatedAt: new Date(),
         })
         .where(eq(copilotChats.id, chatId))
-        .returning({ messages: copilotChats.messages })
+        .returning({ messages: copilotChats.messages, model: copilotChats.model })
 
       if (updated) {
-        await appendCopilotChatMessages(chatId, [userMsg], { streamId: userMessageId })
+        await appendCopilotChatMessages(chatId, [userMsg], {
+          streamId: userMessageId,
+          chatModel: updated.model ?? null,
+        })
       }
 
       const messagesAfter = Array.isArray(updated?.messages) ? updated.messages : undefined

apps/sim/lib/copilot/chat/terminal-state.ts

@@ -49,6 +49,7 @@ export async function finalizeAssistantTurn({
     },
     async (span) => {
       let appendedAssistantMessage: PersistedMessage | undefined
+      let chatModel: string | null = null
       const result = await db.transaction(async (tx) => {
         const where = userId
           ? and(eq(copilotChats.id, chatId), eq(copilotChats.userId, userId))
@@ -58,11 +59,13 @@ export async function finalizeAssistantTurn({
             messages: copilotChats.messages,
             conversationId: copilotChats.conversationId,
             workspaceId: copilotChats.workspaceId,
+            model: copilotChats.model,
           })
           .from(copilotChats)
           .where(where)
           .for('update')
           .limit(1)
+        chatModel = row?.model ?? null
 
         const messages: Record<string, unknown>[] = Array.isArray(row?.messages) ? row.messages : []
         span.setAttribute(TraceAttr.ChatExistingMessageCount, messages.length)
@@ -154,6 +157,7 @@ export async function finalizeAssistantTurn({
       if (appendedAssistantMessage) {
         await appendCopilotChatMessages(chatId, [appendedAssistantMessage], {
           streamId: userMessageId,
+          chatModel,
         })
       }