Make every identity editable: agent and operator names plus avatars

- Migration 049: avatar_emoji/avatar_color on agents and employees
- updateAgent accepts a new name (mention-name validated) and avatar;
  new updateEmployeeProfile renames the operator and sets their avatar
- Avatars are emoji-on-color tiles (renderer CSP blocks remote images);
  an AvatarDirectoryContext built from the snapshot lets the shared
  Avatar component honor custom looks at every call site - chat rows,
  conversation list, org chart, office card, sidebar - without
  threading props through pages
- Team edit dialog gains Name + avatar editor (CEO included); the
  sidebar foot opens an Edit-profile dialog for the operator
- e2e: rename an agent to a new mention handle with an emoji avatar,
  edit the operator profile, both verified in the live shell

src/main/app/ipc-handlers.ts

@@ -135,6 +135,7 @@ export function registerIpcHandlers(deps: IpcDeps): void {
   ipcMain.handle(IPC_CHANNELS.deleteOrganization, (_event, input) => mutate(() => organization.deleteOrganization(input.orgId)));
   ipcMain.handle(IPC_CHANNELS.createAgent, (_event, input) => mutate(() => organization.createAgent(input)));
   ipcMain.handle(IPC_CHANNELS.updateAgent, (_event, input) => mutate(() => organization.updateAgent(input)));
+  ipcMain.handle(IPC_CHANNELS.updateEmployeeProfile, (_event, input) => mutate(() => organization.updateEmployeeProfile(input)));
   ipcMain.handle(IPC_CHANNELS.createTask, (_event, input) => mutate(() => organization.createTask(input)));
   ipcMain.handle(IPC_CHANNELS.updateTask, (_event, input) => mutate(() => organization.updateTask(input)));
   ipcMain.handle(IPC_CHANNELS.deleteTask, (_event, input) => mutate(() => organization.deleteTask(input)));