refactor: merge cycle policy into semantic validation layer

Wire SemanticValidator into the production validator pipeline and
consolidate cycle-policy types under core:validation.

- Add SemanticValidator(CycleExitRule(requirePolicyForCycles=false))
  to the prod ValidationPipeline (no-op default, preserves behavior)
- Move CyclePolicy/Binding/Signature/Factory from core:transitions.policy
  to core:validation.policy (validation already owns ValidationContext)
- Rename CyclePolicyBindingRule -> CycleExitRule (issue code unchanged)
- Delete dead CyclePolicyResolver + PolicyValidation

apps/server/src/main/kotlin/com/correx/apps/server/Main.kt

@@ -35,6 +35,8 @@ import com.correx.core.tools.registry.ToolRegistry
 import com.correx.core.transitions.resolution.DefaultTransitionResolver
 import com.correx.core.validation.artifact.ArtifactPayloadValidator
 import com.correx.core.validation.pipeline.ValidationPipeline
+import com.correx.core.validation.semantic.SemanticValidator
+import com.correx.core.validation.semantic.rules.CycleExitRule
 import com.correx.infrastructure.InfrastructureModule
 import com.correx.infrastructure.artifactscas.DefaultMaterializingArtifactWriter
 import com.correx.infrastructure.inference.DefaultProviderRegistry
@@ -106,7 +108,16 @@ fun main() {
         transitionResolver = DefaultTransitionResolver { condition, ctx -> condition.evaluate(ctx) },
         contextPackBuilder = DefaultContextPackBuilder(DefaultContextCompressor()),
         inferenceRouter = inferenceRouter,
-        validationPipeline = ValidationPipeline(validators = listOf(ArtifactPayloadValidator(artifactStore))),
+        validationPipeline = ValidationPipeline(
+            validators = listOf(
+                ArtifactPayloadValidator(artifactStore),
+                SemanticValidator(
+                    rules = listOf(
+                        CycleExitRule(requirePolicyForCycles = false),
+                    ),
+                ),
+            ),
+        ),
         approvalEngine = approvalEngine,
         riskAssessor = DefaultRiskAssessor(),
         promptResolver = { path -> InfrastructureModule.createPromptLoader().load(path) },