fix(BUG-8): ws adapter auto-reconnect after drop

WS adapter had no reconnect. WS dies (idle/error/close) → wsReady=null,
subscribers dead forever, display frozen until full reload.

Changes (src/storage/ws.js):
- onClose: schedule reconnect via setTimeout(500ms), ensureWs re-arms.
  Guard: disposed flag stops reconnect after dispose.
- onOpen: resubscribe all existing doc/coll subscribers (backend state
  may have changed). Re-fetch current values on RECONNECT only (skip
  first connect — initial REST fetch in subscribe* already did). Added
  everConnected flag to distinguish first vs reconnect.
- reconnectTimer unref'd (Node) to avoid hanging event loop.
- dispose(cb): set disposed, clear timer, close ws, then cb.

Also fixed test teardown leaks:
- server/index.js close(): terminate all wss.clients before wss.close().
  Reconnect test spawned new ws to server; old close hung on live conn.
- both ws test factories: port 0 (OS picks free) instead of module-local
  nextPort counter. Parallel jest workers collided on EADDRINUSE.

Tests: ws-reconnect GREEN (1.7s), ws-contract 23 GREEN. No regression.
server suite 24/24. shared 90/90.

server/index.js

@@ -131,7 +131,11 @@ function createServer({ dbPath, port, corsOrigin } = {}) {
 
   return {
     app, server, wss, store, db,
-    close(done) { wss.close(); server.close(() => { db.close(); if (done) done(); }); },
+    close(done) {
+      wss.clients.forEach(c => { try { c.terminate(); } catch {} });
+      wss.close();
+      server.close(() => { db.close(); if (done) done(); });
+    },
   };
 }