decomposenavigator-testing

Test doubles for decomposenavigator-core: FakeLineNavigator and FakeSwitchNavigator are real in-memory implementations (not call recorders over a no-op) that mutate their stack the way the Decompose-backed navigators do, so a test can push/pop/switch through them and assert on the result. FakeDeepLinkNavigator doubles the DeepLinkNavigator seam for testing DeepLinkHandler implementations without Decompose or Compose on the classpath. RecordingNavigator is a minimal concrete Navigator for exercising the navigator-tree traversal and lifecycle logic directly. Pick this module when writing unit tests for code that navigates.