feat(fleet): add reviewed v1-to-v2 migration preview (#788)

packages/mosaic/src/fleet/roster-v2.spec.ts

@@ -45,6 +45,12 @@ agents:
 
 let semanticTmp: string | undefined;
 
+it('preserves an explicit empty socket as the literal default tmux server', () => {
+  const roster = parseRosterV2(validRoster.replace('socket_name: mosaic-fleet', "socket_name: ''"));
+  expect(roster.tmux.socketName).toBe('');
+  expect(renderRosterV2Yaml(roster)).toContain('socket_name: ""');
+});
+
 afterEach(async (): Promise<void> => {
   if (semanticTmp) await rm(semanticTmp, { recursive: true, force: true });
   semanticTmp = undefined;