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ApprovalRoutes (never registered), TuiNavigation (superseded by reducer),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.

core/transitions/src/main/kotlin/com/correx/core/transitions/execution/StageExecutor.kt

@@ -1,7 +0,0 @@
-package com.correx.core.transitions.execution
-
-interface StageExecutor {
-    fun execute(
-        request: StageExecutionRequest
-    ): StageExecutionResult
-}

core/transitions/src/main/kotlin/com/correx/core/transitions/policy/CyclePolicyResolver.kt

@@ -1,12 +0,0 @@
-package com.correx.core.transitions.policy
-
-class CyclePolicyResolver(
-    private val bindings: Set<CyclePolicyBinding>
-) {
-
-    fun resolve(signature: CycleSignature): CyclePolicy? {
-        return bindings
-            .firstOrNull { it.cycle == signature }
-            ?.policy
-    }
-}

core/transitions/src/main/kotlin/com/correx/core/transitions/policy/PolicyValidation.kt

@@ -1,23 +0,0 @@
-package com.correx.core.transitions.policy
-
-class PolicyValidation {
-    fun validate(
-        bindings: Set<CyclePolicyBinding>,
-        knownCycles: Set<CycleSignature>
-    ): List<String> {
-
-        val errors = mutableListOf<String>()
-
-        val bound = bindings.map { it.cycle }.toSet()
-
-        val unbound = knownCycles - bound
-
-        if (unbound.isNotEmpty()) {
-            errors += unbound.map {
-                "Cycle $it has no policy binding"
-            }
-        }
-
-        return errors
-    }
-}