fix(dispatcher): surface preg_match() engine failures instead of treating them as no-match

All dispatcher strategies checked preg_match() results with `!== 1`,
which conflates a genuine no-match (0) with a PCRE engine failure
(false), e.g. PREG_BACKTRACK_LIMIT_ERROR from a catastrophically
backtracking route pattern. Because dynamic routes for the same
method are combined into shared regex chunks, one such route could
make the preg_match() call for the whole chunk fail, silently
turning an unrelated, cheap route in that chunk into a spurious
NOT_FOUND.

Add a shared matchRoute() helper on RegexBasedAbstract that calls
preg_match() and throws a RuntimeException (including
preg_last_error_msg()) when it returns false, while preserving the
existing 0/1 no-match/match behavior. Update GroupCountBased,
GroupPosBased, CharCountBased and MarkBased to use it.

Fixes #167

src/Dispatcher/RegexBasedAbstract.php

@@ -8,6 +8,11 @@ use FastRoute\Dispatcher;
 use FastRoute\Dispatcher\Result\Matched;
 use FastRoute\Dispatcher\Result\MethodNotAllowed;
 use FastRoute\Dispatcher\Result\NotMatched;
+use RuntimeException;
+
+use function preg_last_error_msg;
+use function preg_match;
+use function sprintf;
 
 /**
  * @internal
@@ -35,6 +40,33 @@ abstract class RegexBasedAbstract implements Dispatcher
     /** @param DynamicRouteChunks $routeData */
     abstract protected function dispatchVariableRoute(array $routeData, string $uri): ?Matched;
 
+    /**
+     * Matches a compiled route regex against the subject, distinguishing a
+     * genuine "no match" (preg_match() returning 0) from a PCRE engine
+     * failure (preg_match() returning false).
+     *
+     * A regex engine failure - for example PREG_BACKTRACK_LIMIT_ERROR caused
+     * by a catastrophically backtracking route pattern - must not be treated
+     * as "no match". Silently swallowing it can make an unrelated, cheap
+     * route that happens to share the same combined regex chunk spuriously
+     * fail to match.
+     *
+     * @see https://github.com/nikic/FastRoute/issues/167
+     *
+     * @param array<int|string, mixed>|null $matches
+     */
+    protected function matchRoute(string $regex, string $subject, ?array &$matches = null): int
+    {
+        $result = preg_match($regex, $subject, $matches);
+        if ($result === false) {
+            throw new RuntimeException(
+                sprintf('Regex matching failed for "%s": %s', $regex, preg_last_error_msg()),
+            );
+        }
+
+        return $result;
+    }
+
     public function dispatch(string $httpMethod, string $uri): Matched|NotMatched|MethodNotAllowed
     {
         if (isset($this->staticRouteMap[$httpMethod][$uri])) {