Merge PR #149 from aakhter/cod-165-ws-resilience: WebSocket durable-delivery resilience

Includes review fixes: real _wsState lifecycle (connecting/connected/disconnected), per-tab supersede identity (multi-tab coexistence), preserved reconnect backoff, connection-dot CSS for connected/fallback states.

src/web/public/constants.js

@@ -156,6 +156,30 @@ function shouldAutoWrapTabs(input) {
   return scrollWidth > clientWidth + 1;
 }
 
+// COD-134 — Terminal WebSocket reconnect policy.
+//
+// Decide what to do after a terminal WebSocket closes, given the close `code`
+// and `attempt` (0-based count of consecutive reconnects already made):
+//   - transient closes (code < 4004: 1000/1001/1005/1006/etc.) → 'reconnect'
+//     with exponential backoff (0 on the first attempt; the caller adds jitter),
+//     250ms → 500 → 1000 → ... capped at 10s.
+//   - 4004 (session not found) / 4009 (session terminated) → 'give-up': the
+//     session is gone, retrying only wastes connections.
+//   - 4008 (too many connections) and any other code >= 4004 → 'retry-fallback':
+//     show the HTTP fallback but keep retrying on a bounded 5s timer so the
+//     transport returns to WS once the transient condition clears (un-stick).
+// Pure: no DOM, no side effects.
+function planWsReconnect(code, attempt) {
+  if (code === 4004 || code === 4009) {
+    return { action: 'give-up', delayMs: 0 };
+  }
+  if (code >= 4004) {
+    return { action: 'retry-fallback', delayMs: 5000 };
+  }
+  const delayMs = attempt <= 0 ? 0 : Math.min(250 * Math.pow(2, attempt - 1), 10000);
+  return { action: 'reconnect', delayMs };
+}
+
 if (typeof window !== 'undefined') {
   window.WEBGL_FALLBACK = WEBGL_FALLBACK;
   window.evaluateWebGLLongTaskTrip = evaluateWebGLLongTaskTrip;
@@ -163,6 +187,9 @@ if (typeof window !== 'undefined') {
   window.CodemanTabOverflow = {
     shouldAutoWrapTabs,
   };
+  window.CodemanWsReconnect = {
+    plan: planWsReconnect,
+  };
 }
 
 // Scheduler API — prioritize terminal writes over background UI updates.