feat(artifacts): config-driven custom artifact kinds with schema validation

Users declare artifact kinds in [[artifacts]] (id + schema_path to a JSON-schema file + llm_emitted); ConfigArtifactKind registers them at startup via createWorkflowLoader(extraKinds). New JsonSchemaValidator validates any non-built-in kind generically against its declared deriveJsonSchema(), so an LLM-emitted custom kind is checked against its shape, never trusted. Removed the dead payloadSerializer from the ArtifactKind contract. Schema source is path-to-file (not inline TOML — the hand-rolled parser can't nest).

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

@@ -4,6 +4,9 @@ import com.correx.apps.server.logging.LoggingEventStore
 import com.correx.apps.server.registry.FileSystemWorkflowRegistry
 import com.correx.apps.server.registry.ProviderRegistry
 import com.correx.core.approvals.domain.DefaultApprovalEngine
+import com.correx.core.artifacts.kind.ArtifactKind
+import com.correx.core.artifacts.kind.ConfigArtifactKind
+import com.correx.core.artifacts.kind.JsonSchema
 import com.correx.core.artifactstore.ArtifactStore
 import com.correx.core.config.ConfigLoader
 import com.correx.core.config.CorrexConfig
@@ -62,7 +65,9 @@ import com.correx.infrastructure.tools.ToolConfig
 import io.ktor.server.engine.embeddedServer
 import io.ktor.server.netty.Netty
 import kotlinx.coroutines.runBlocking
+import kotlinx.serialization.json.Json
 import org.slf4j.LoggerFactory
+import java.nio.file.Files
 import java.nio.file.Path
 import java.nio.file.Paths
 
@@ -244,7 +249,9 @@ fun main() {
         eventStore = eventStore,
         artifactStore = artifactStore,
         sessionRepository = repositories.sessionRepository,
-        workflowRegistry = FileSystemWorkflowRegistry(InfrastructureModule.createWorkflowLoader()),
+        workflowRegistry = FileSystemWorkflowRegistry(
+            InfrastructureModule.createWorkflowLoader(loadConfigArtifactKinds(correxConfig)),
+        ),
         providerRegistry = infraRegistry.asServerRegistry(),
         defaultOrchestrationConfig = defaultOrchestrationConfig,
         routerFacade = routerFacade,
@@ -294,6 +301,39 @@ private fun logStoresInfo(
     log.info("  artifact store: {}", artifactStore::class.simpleName)
 }
 
+// Build user-declared artifact kinds from config. Each [[artifacts]] entry points to a JSON
+// schema file; we parse it into a JsonSchema and wrap it in a ConfigArtifactKind. A schema that
+// can't be loaded is skipped with a warning — any workflow that references the kind then fails
+// loudly at load time ("Unknown artifact kind"), rather than running with an unvalidated kind.
+private fun loadConfigArtifactKinds(config: CorrexConfig): List<ArtifactKind> {
+    val configDir = ConfigLoader.configPath().parent
+    return config.artifacts.mapNotNull { decl ->
+        val schemaPath = resolveConfigRelativePath(decl.schemaPath, configDir)
+        val schema = runCatching {
+            Json.decodeFromString(JsonSchema.serializer(), Files.readString(schemaPath))
+        }.getOrElse { e ->
+            System.err.println(
+                "Warning: artifact kind '${decl.id}' schema '$schemaPath' failed to load: ${e.message}",
+            )
+            return@mapNotNull null
+        }
+        ConfigArtifactKind(id = decl.id, schema = schema, llmEmitted = decl.llmEmitted)
+    }
+}
+
+private fun resolveConfigRelativePath(raw: String, configDir: Path?): Path {
+    val expanded = if (raw.startsWith("~/")) {
+        Paths.get(System.getProperty("user.home"), raw.removePrefix("~/"))
+    } else {
+        Path.of(raw)
+    }
+    return when {
+        expanded.isAbsolute -> expanded
+        configDir != null -> configDir.resolve(expanded)
+        else -> expanded
+    }
+}
+
 private fun buildProviders(config: CorrexConfig): List<LlamaCppInferenceProvider> {
     return if (config.providers.isNotEmpty()) {
         log.info("Loading {} provider(s) from config", config.providers.size)