Task #42: Tell members when someone leaves a group on their own

Original task: Post a bilingual system message into the group chat
when a member leaves via POST /api/conversations/:id/leave, with
real-time delivery via Socket.IO and rendering in the chat thread.

Findings:
- The leave handler in artifacts/api-server/src/routes/conversations.ts
  already inserts a `member_left` system message (and `admin_promoted`
  when a successor is auto-promoted) and emits via Socket.IO using
  insertAndEmitSystemMessage. Direct conversations and last-leaver
  cleanup paths are correctly skipped.
- artifacts/teaboy-os/src/pages/chat.tsx renderSystemMessage already
  handles `member_left`, `admin_promoted`, and `adminPromotedAfterLeave`.
- Bilingual locale keys exist in src/locales/en.json and ar.json under
  chat.system.memberLeft / adminPromoted / adminPromotedAfterLeave.

Change made:
- Extended the MessageWithSender.kind enum in lib/api-spec/openapi.yaml
  to include `member_left` and `admin_promoted` (previously only
  user/group_renamed/members_added/member_removed were declared).
- Re-ran `pnpm --filter @workspace/api-spec run codegen` to regenerate
  api-zod and api-client-react schemas so the spec, runtime validation,
  and client types stay in sync.
- Verified `pnpm -w run typecheck` passes across all packages.

No behavioural code changes were necessary; the feature was already
implemented end-to-end and only the API spec enum needed to catch up.

Replit-Task-Id: 40fccb3a-4fc0-4ad7-a6e9-d1ac67ef7769

lib/api-client-react/src/generated/api.schemas.ts

@@ -269,6 +269,8 @@ export const MessageWithSenderKind = {
   group_renamed: "group_renamed",
   members_added: "members_added",
   member_removed: "member_removed",
+  member_left: "member_left",
+  admin_promoted: "admin_promoted",
 } as const;
 
 export type MessageWithSenderMeta = { [key: string]: unknown } | null;

lib/api-spec/openapi.yaml

@@ -1708,7 +1708,7 @@ components:
           type: string
         kind:
           type: string
-          enum: [user, group_renamed, members_added, member_removed]
+          enum: [user, group_renamed, members_added, member_removed, member_left, admin_promoted]
         meta:
           type: object
           nullable: true

lib/api-zod/src/generated/api.ts

@@ -596,6 +596,8 @@ export const ListConversationsResponseItem = zod.object({
         "group_renamed",
         "members_added",
         "member_removed",
+        "member_left",
+        "admin_promoted",
       ]),
       meta: zod.record(zod.string(), zod.unknown()).nullish(),
       sender: zod.object({
@@ -666,6 +668,8 @@ export const GetConversationResponse = zod.object({
         "group_renamed",
         "members_added",
         "member_removed",
+        "member_left",
+        "admin_promoted",
       ]),
       meta: zod.record(zod.string(), zod.unknown()).nullish(),
       sender: zod.object({
@@ -728,6 +732,8 @@ export const UpdateConversationResponse = zod.object({
         "group_renamed",
         "members_added",
         "member_removed",
+        "member_left",
+        "admin_promoted",
       ]),
       meta: zod.record(zod.string(), zod.unknown()).nullish(),
       sender: zod.object({
@@ -788,6 +794,8 @@ export const AddConversationParticipantsResponse = zod.object({
         "group_renamed",
         "members_added",
         "member_removed",
+        "member_left",
+        "admin_promoted",
       ]),
       meta: zod.record(zod.string(), zod.unknown()).nullish(),
       sender: zod.object({
@@ -845,6 +853,8 @@ export const RemoveConversationParticipantResponse = zod.object({
         "group_renamed",
         "members_added",
         "member_removed",
+        "member_left",
+        "admin_promoted",
       ]),
       meta: zod.record(zod.string(), zod.unknown()).nullish(),
       sender: zod.object({
@@ -906,6 +916,8 @@ export const UpdateConversationStateResponse = zod.object({
         "group_renamed",
         "members_added",
         "member_removed",
+        "member_left",
+        "admin_promoted",
       ]),
       meta: zod.record(zod.string(), zod.unknown()).nullish(),
       sender: zod.object({
@@ -950,7 +962,14 @@ export const ListMessagesResponseItem = zod.object({
   conversationId: zod.number(),
   senderId: zod.number(),
   content: zod.string(),
-  kind: zod.enum(["user", "group_renamed", "members_added", "member_removed"]),
+  kind: zod.enum([
+    "user",
+    "group_renamed",
+    "members_added",
+    "member_removed",
+    "member_left",
+    "admin_promoted",
+  ]),
   meta: zod.record(zod.string(), zod.unknown()).nullish(),
   sender: zod.object({
     id: zod.number(),