Promote AgentCompany-New to the repository root and retire the old app

The legacy application - its src, tests, landing site, promo assets, docs,
release tooling, CI workflows, and root configs - leaves the tree; it stays
reachable in history. Everything under AgentCompany-New moves up unchanged:
same package name, so the production userData/database path is untouched,
and e2e/build scripts already resolved paths relative to the project. The
developer cred.txt stays gitignored at its new location. Full verify:ci
passes from the new root.

src/shared/chat-domain.ts

@@ -0,0 +1,91 @@
+import type { ChatThreadBoardState } from "./board-domain";
+
+export interface ChatSpaceRecord {
+  id: string;
+  orgId: string;
+  spaceType: string;
+  name: string;
+  topic: string;
+  visibility: string;
+  retentionPolicy: string;
+  createdAt: string;
+}
+
+export interface ChatMessageRecord {
+  id: string;
+  orgId: string;
+  spaceId: string;
+  threadId: string | null;
+  senderType: "employee" | "agent" | "board" | "system";
+  senderId: string | null;
+  bodyMd: string;
+  bodyStructuredJson: string;
+  deliveryState: string;
+  createdAt: string;
+  editedAt: string | null;
+  deletedAt: string | null;
+}
+
+export interface ChatMembershipRecord {
+  spaceId: string;
+  principalType: "employee" | "agent";
+  principalId: string;
+  role: string;
+  muteState: string;
+}
+
+export interface ChatThreadRecord {
+  id: string;
+  orgId: string;
+  spaceId: string;
+  rootMessageId: string | null;
+  title: string;
+  state: string;
+  boardState: ChatThreadBoardState;
+  controlledByType: "employee" | "agent" | "board" | null;
+  controlledById: string | null;
+  createdAt: string;
+  updatedAt: string;
+}
+
+export interface ChatAttachmentRecord {
+  messageId: string;
+  fileId: string;
+  transferType: string;
+  checksum: string;
+  previewKey: string | null;
+}
+
+export interface ChatMentionRecord {
+  messageId: string;
+  targetType: "employee" | "agent" | "board" | "org_group";
+  targetId: string;
+  offsetStart: number;
+  offsetEnd: number;
+  wakeState: "none" | "woken" | "failed";
+}
+
+export interface ChatSlashInvocationRecord {
+  id: string;
+  messageId: string;
+  command: string;
+  argsJson: string;
+  resultRef: string | null;
+  createdAt: string;
+}
+
+export interface ChatPresenceRecord {
+  principalType: string;
+  principalId: string;
+  status: string;
+  statusText: string;
+  lastSeenAt: string;
+}
+
+export interface ChatReadStateRecord {
+  orgId: string;
+  employeeId: string;
+  spaceId: string;
+  lastReadMessageId: string | null;
+  lastReadAt: string;
+}