feat(kernel,server): rehydrate() + POST /sessions/{id}/resume

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

@@ -188,6 +188,25 @@ class ServerModule(
         }
     }
 
+    /**
+     * Rehydrates [artifactContentCache] from durable events and then resumes the session.
+     * Called by [POST /sessions/{id}/resume] to restart a session after a server restart
+     * without re-running already-completed stages.
+     */
+    fun launchSessionResumeWithRehydrate(sessionId: SessionId, graph: com.correx.core.transitions.graph.WorkflowGraph) {
+        activeSessionJobs.computeIfAbsent(sessionId) {
+            moduleScope.launch {
+                runCatching {
+                    orchestrator.rehydrate(sessionId)
+                    orchestrator.resume(sessionId, graph, defaultOrchestrationConfig)
+                }.onFailure { e ->
+                    log.error("resumeSession (rehydrate): session={} failed", sessionId.value, e)
+                }
+                activeSessionJobs.remove(sessionId)
+            }
+        }
+    }
+
     private fun resumeAbandonedSessions() {
         eventStore.allSessionIds().forEach { sessionId ->
             val orchState = orchestrationRepository.getState(sessionId)

apps/server/src/main/kotlin/com/correx/apps/server/routes/SessionRoutes.kt

@@ -43,6 +43,7 @@ fun Route.sessionRoutes(module: ServerModule) {
             getSessionRoute(module)
             cancelSessionRoute(module)
             undoSessionRoute(module)
+            resumeSessionRoute(module)
             getEventsRoute(module)
             webSocket("/stream") {
                 val id = call.parameters["id"] ?: return@webSocket
@@ -98,6 +99,21 @@ private fun Route.undoSessionRoute(module: ServerModule) {
     }
 }
 
+private fun Route.resumeSessionRoute(module: ServerModule) {
+    post("/resume") {
+        val id = call.parameters["id"]
+            ?: return@post call.respond(HttpStatusCode.BadRequest, "Missing session id")
+        val orchState = runCatching { module.orchestrationRepository.getState(TypeId(id)) }.getOrNull()
+            ?: return@post call.respond(HttpStatusCode.NotFound, "Session not found")
+        val workflowId = orchState.workflowId.takeIf { it.isNotBlank() }
+            ?: return@post call.respond(HttpStatusCode.BadRequest, "Session has no workflowId")
+        val graph = module.workflowRegistry.find(workflowId)
+            ?: return@post call.respond(HttpStatusCode.BadRequest, "Unknown workflowId: $workflowId")
+        module.launchSessionResumeWithRehydrate(TypeId(id), graph)
+        call.respond(HttpStatusCode.Accepted)
+    }
+}
+
 private fun Route.getEventsRoute(module: ServerModule) {
     get("/events") {
         val id = call.parameters["id"]