tests: replace QTest::qWait(N) with signal-based waits

Fixed-time sleeps are a source of intermittent failures on slow CI
machines — if the delay is too short, the test races ahead of the
code under test.

Replacements made:
- dolphinmainwindowtest: qWait() calls replaced with QTRY_COMPARE,
  QTRY_VERIFY, qWaitFor lambdas and processEvents() where animations
  are disabled; one genuinely unavoidable timer wait marked
  // UNAVOIDABLE:
- kitemlistcontrollerexpandtest: qWaitFor(..., 100ms) / qWaitFor(...,
  300ms) replaced with spy->wait() loops that block until all
  expected directoryLoadingCompleted signals have arrived
- kitemlistkeyboardsearchmanagertest: timer-driven wait marked
  // UNAVOIDABLE: (must wait for keyboard search timeout to expire)

Add testhelpers.h providing TestHelpers::disableAnimations(), which
eliminates the need for delays that previously waited for Qt UI
animations to settle.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/tests/kitemlistkeyboardsearchmanagertest.cpp b/src/tests/kitemlistkeyboardsearchmanagertest.cpp
index feba6acba..601576102 100644
--- a/src/tests/kitemlistkeyboardsearchmanagertest.cpp
+++ b/src/tests/kitemlistkeyboardsearchmanagertest.cpp
@@ -137,7 +137,7 @@ void KItemListKeyboardSearchManagerTest::testAbortedKeyboardSearch()
 
     // If the delay between two key presses is larger than the chosen timeout,
     // a new search is started. We add a small safety margin to avoid race conditions.
-    QTest::qWait(m_keyboardSearchManager.timeout() + 10);
+    QTest::qWait(m_keyboardSearchManager.timeout() + 10); // UNAVOIDABLE: must wait for keyboard search timeout to expire
 
     m_keyboardSearchManager.addKeys("l");
     verifySignal(spy, "l", true);