chore(cleanup): delete confirmed-dead files with no live references

Removes 6 files audited as fully unused: StageExecutor interface (shadowed
by kernel), CyclePolicyResolver and PolicyValidation (deferred cycle policy),
ApprovalRoutes (never registered), TuiNavigation (superseded by reducer),
and ReplayContractTest abstract class (no concrete subclasses).

ArtifactRelationshipType and CyclePolicy were audited but retained —
both are actively referenced by production code.

testing/contracts/src/testFixtures/kotlin/com/correx/testing/contracts/fixtures/projections/ReplayContractTest.kt

@@ -1,35 +0,0 @@
-package com.correx.testing.contracts.fixtures.projections
-
-import com.correx.core.events.stores.EventStore
-import com.correx.core.events.types.EventId
-import com.correx.core.events.types.SessionId
-import com.correx.core.sessions.projections.replay.EventReplayer
-import com.correx.testing.fixtures.EventFixtures.newEvent
-import kotlinx.coroutines.runBlocking
-import org.junit.jupiter.api.Assertions.assertEquals
-import org.junit.jupiter.api.Test
-
-abstract class ReplayContractTest<S> {
-
-    protected abstract fun store(): EventStore
-
-    protected abstract fun replayer(
-        store: EventStore
-    ): EventReplayer<S>
-
-    @Test
-    fun `rebuild is deterministic`(): Unit = runBlocking {
-        val store = store()
-
-        repeat(50) {
-            store.append(newEvent(EventId("e$it"), SessionId("s1")))
-        }
-
-        val replayer = replayer(store)
-
-        val state1 = replayer.rebuild(SessionId("s1"))
-        val state2 = replayer.rebuild(SessionId("s1"))
-
-        assertEquals(state1, state2)
-    }
-}