v3: chatbox improvements (typing indicators, answer to previous messages, backlog days separators, scroll to last message position, visual tweaks)

api/model/db.ts

@@ -313,6 +313,12 @@ export interface ChatMessageRow {
   updated_at: string | null;
   author_username: string;
   author_avatar_mime: string | null;
+  // Reply columns: reply_to_id is the stored target; the author/body preview are
+  // LEFT-JOINed from the target and go null when there's no reply (or it was
+  // since deleted).
+  reply_to_id: string | null;
+  reply_to_author: string | null;
+  reply_to_body: string | null;
   [key: string]: SQLOutputValue;
 }
 
@@ -327,7 +333,13 @@ export function isChatMessageRow(obj: unknown): obj is ChatMessageRow {
     "author_username" in obj && typeof obj.author_username === "string" &&
     "author_avatar_mime" in obj &&
     (typeof obj.author_avatar_mime === "string" ||
-      obj.author_avatar_mime === null);
+      obj.author_avatar_mime === null) &&
+    "reply_to_id" in obj &&
+    (typeof obj.reply_to_id === "string" || obj.reply_to_id === null) &&
+    "reply_to_author" in obj &&
+    (typeof obj.reply_to_author === "string" || obj.reply_to_author === null) &&
+    "reply_to_body" in obj &&
+    (typeof obj.reply_to_body === "string" || obj.reply_to_body === null);
 }
 
 export function chatMessageRowToApi(row: ChatMessageRow): ChatMessage {
@@ -339,6 +351,9 @@ export function chatMessageRowToApi(row: ChatMessageRow): ChatMessage {
     updatedAt: row.updated_at ? new Date(row.updated_at) : undefined,
     authorUsername: row.author_username,
     authorAvatarMime: row.author_avatar_mime ?? undefined,
+    replyToId: row.reply_to_id ?? undefined,
+    replyToAuthor: row.reply_to_author ?? undefined,
+    replyToBody: row.reply_to_body ?? undefined,
   };
 }