fix: Pool setTimeout state tracking and MySQL timeout dirty flag

- Pool::setTimeout() now stores timeout locally so delegate() correctly
  propagates it to child adapters on subsequent calls
- MySQL timeout uses dirty flag to only issue SET SESSION MAX_EXECUTION_TIME
  when timeout state actually changes, avoiding overhead on every query
- MySQL::clearTimeout() marks dirty flag so the next execute() clears
  the session variable

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: abnegate

src/Database/Adapter/MySQL.php

@@ -54,6 +54,8 @@ public function capabilities(): array
      *
      * @throws DatabaseException
      */
+    private bool $timeoutDirty = false;
+
     public function setTimeout(int $milliseconds, Event $event = Event::All): void
     {
         if (! $this->supports(Capability::Timeouts)) {
@@ -64,11 +66,23 @@ public function setTimeout(int $milliseconds, Event $event = Event::All): void
         }
 
         $this->timeout = $milliseconds;
+        $this->timeoutDirty = true;
+    }
+
+    public function clearTimeout(Event $event = Event::All): void
+    {
+        if ($this->timeout > 0) {
+            $this->timeoutDirty = true;
+        }
+        $this->timeout = 0;
     }
 
     protected function execute(mixed $stmt): bool
     {
-        $this->getPDO()->exec("SET SESSION MAX_EXECUTION_TIME = {$this->timeout}");
+        if ($this->timeoutDirty) {
+            $this->getPDO()->exec("SET SESSION MAX_EXECUTION_TIME = {$this->timeout}");
+            $this->timeoutDirty = false;
+        }
         /** @var PDOStatement|\Swoole\Database\PDOStatementProxy $stmt */
         return $stmt->execute();
     }

src/Database/Adapter/Pool.php

@@ -151,6 +151,7 @@ public function removeQueryTransform(string $name): static
      */
     public function setTimeout(int $milliseconds, Event $event = Event::All): void
     {
+        $this->timeout = $milliseconds;
         $this->delegate(__FUNCTION__, \func_get_args());
     }