docs(auth-utils): document intentional inconsistent state in destroy()

Addresses Copilot AI comment on PR #79 about unclear behavior when destroy()
returns early due to locked mutexes.

Problem:
When destroy() is called but mutexes are locked (active transactions), the
function sets destroyed=true but returns early without destroying resources.
This creates temporary inconsistent state that wasn't documented, making it
unclear if this was intentional or a bug.

Behavior:
1. destroy() ALWAYS sets destroyed=true (prevents new transactions)
2. If mutexes locked: early return, resources NOT destroyed
3. Active transactions continue safely with existing resources
4. After transactions complete: resources cleaned up by GC
5. If no locked mutexes: resources destroyed immediately

State during early return:
- destroyed = true (new transactions throw error)
- preKeyManager exists (active transactions can use it)
- keyQueues exist (active transactions can use them)

This is INTENTIONAL and SAFE:
- New transactions are rejected (destroyed flag check)
- Active transactions complete successfully (resources exist)
- No crash, no corruption, just deferred cleanup

Changes:
- Added comprehensive JSDoc explaining the two-path behavior
- Documented the intentional temporary inconsistent state
- Added inline comment reminding that flag is set even on early return
- Clarified that GC handles cleanup for early return case

This addresses the Copilot concern that the behavior was misleading.
The state is intentional, not a bug - just needed documentation.

https://claude.ai/code/session_VMxqX

src/Utils/auth-utils.ts

@@ -353,9 +353,19 @@ export const addTransactionCapability = (
 		/**
 		 * Cleanup all resources (queues, managers, mutexes)
 		 * Should be called during connection cleanup
+		 *
+		 * IMPORTANT BEHAVIOR:
+		 * - Always sets destroyed=true to prevent NEW transactions
+		 * - If mutexes are locked (active transactions), returns early WITHOUT destroying resources
+		 * - This creates intentional temporary inconsistent state:
+		 *   * destroyed=true (new transactions rejected)
+		 *   * resources exist (active transactions complete safely)
+		 *   * resources cleaned up by GC after active transactions finish
+		 * - If no locked mutexes, destroys resources immediately
 		 */
 		destroy: () => {
 			// CRITICAL: Set destroyed flag FIRST to prevent new transactions
+			// Note: Flag is set even if early return occurs (see doc above)
 			destroyed = true
 			logger.debug('🗑️ Cleaning up transaction capability resources')