fix(gotchas-memory): apply errorWindowMs window and fix critical sort order

Two bugs in GotchasMemory:

1. trackError() never applied the errorWindowMs rolling window (fixes #475).
   Errors accumulated indefinitely — the 24-hour window config was dead code.
   Fix: reset the count when the elapsed time since lastSeen exceeds the window.

2. listGotchas() used `|| 2` fallback on severityOrder, causing `critical` (= 0)
   to be treated as falsy and sorted last instead of first (fixes #476).
   Fix: use `?? 2` (nullish coalescing) to preserve the zero value.

60 unit tests added covering all public methods, error window regression,
sort correctness, persistence, and event emission.

Author: nikolasdehor

.aiox-core/core/memory/gotchas-memory.js

@@ -257,6 +257,12 @@ class GotchasMemory extends EventEmitter {
         errorPattern: errorData.message,
         category: this._detectCategory(errorData.message + ' ' + (errorData.stack || '')),
       };
+    } else if (now - tracking.lastSeen >= this.options.errorWindowMs) {
+      // Window expired — reset count so only errors within the rolling window
+      // contribute toward the auto-capture threshold (fixes #475)
+      tracking.count = 0;
+      tracking.firstSeen = now;
+      tracking.samples = [];
     }
 
     // Update tracking
@@ -311,10 +317,13 @@ class GotchasMemory extends EventEmitter {
       gotchas = gotchas.filter((g) => !g.resolved);
     }
 
-    // Sort by severity (critical first), then by last occurrence
+    // Sort by severity (critical first), then by last occurrence.
+    // Use ?? not || so that 0 (critical) is not treated as falsy (fixes #476)
     const severityOrder = { critical: 0, warning: 1, info: 2 };
     gotchas.sort((a, b) => {
-      const severityDiff = (severityOrder[a.severity] || 2) - (severityOrder[b.severity] || 2);
+      const aSev = severityOrder[a.severity] ?? 2;
+      const bSev = severityOrder[b.severity] ?? 2;
+      const severityDiff = aSev - bSev;
       if (severityDiff !== 0) return severityDiff;
       return new Date(b.source.lastSeen) - new Date(a.source.lastSeen);
     });