refactor: apply the Rector stage-2 pass and keep its helpers reachable from tests

Mechanical output of `make rector-fix` over the class-based trees, reviewed
change by change. Most of it is empty()/=== [] normalisation, a chained === turned
into in_array(..., true) in FanoutConfig, and multi-line condition reformatting.

Three changes were checked more closely because they looked behaviour-affecting:

- Translator::isRtl() loses its (string) cast on $lang. Safe: $currentLang is a
  non-nullable `private static string`, so the ??= above always leaves a string.
- TableController loses htmlValue() and jsArgument(). They are escaping helpers,
  so the removal was verified rather than trusted: neither has a single reference
  anywhere under src/, views included. Genuinely dead.
- StartupCommand and StreamsCronJob have three private helpers turned from static
  into instance methods (LocallyCalledStaticMethodToNonStatic).

That last one broke 7 tests, which reached the helpers through Reflection and
invoked them statically. Fixed in the tests rather than by reverting the rule —
reverting would only lose the argument again on the next `make rector-fix`. The
Reflection helpers now bind an instance only when the method needs one, so they
survive the flip in either direction.

Also re-ran the two KNOWN BUG greps from build/rector.php (the rules that drop
parens around an assignment-in-condition and invert the guard): both clean.

Verified: 857 tests, make gates, make cs, CRAP gate.

tests/Unit/StartupCommandRuntimeFilesTest.php

@@ -12,10 +12,15 @@ final class StartupCommandRuntimeFilesTest extends TestCase {
 
 	private string $dir;
 
+	/**
+	 * Call a private helper. Whether it is static is an implementation detail
+	 * (Rector's LocallyCalledStaticMethodToNonStatic flips it), so bind an
+	 * instance only when the method actually needs one.
+	 */
 	private function call(string $rMethod, ...$rArgs) {
 		$rM = new ReflectionMethod(StartupCommand::class, $rMethod);
 		$rM->setAccessible(true);
-		return $rM->invoke(null, ...$rArgs);
+		return $rM->invoke($rM->isStatic() ? null : new StartupCommand(), ...$rArgs);
 	}
 
 	protected function setUp(): void {