fix(agents): enforce Sisyphus->Hephaestus->Prometheus->Atlas assembly order

Extract hephaestus into agentConfig before prometheus so the config
handler naturally assembles agents in the canonical order instead of
relying solely on reorderAgentsByPriority to fix the wrong intermediate
order. Also fix test data that had atlas/prometheus swapped and add
missing hephaestus to agent-config-integration test lists.

src/plugin-handlers/agent-config-handler.ts

@@ -163,10 +163,15 @@ export async function applyAgentConfig(params: {
         getAgentDisplayName("sisyphus");
     }
 
+    // Assembly order: Sisyphus -> Hephaestus -> Prometheus -> Atlas
     const agentConfig: Record<string, unknown> = {
       sisyphus: builtinAgents.sisyphus,
     };
 
+    if (builtinAgents.hephaestus) {
+      agentConfig["hephaestus"] = builtinAgents.hephaestus;
+    }
+
     agentConfig["sisyphus-junior"] = createSisyphusJuniorAgentWithOverrides(
       params.pluginConfig.agents?.["sisyphus-junior"],
       (builtinAgents.atlas as { model?: string } | undefined)?.model,
@@ -248,7 +253,7 @@ export async function applyAgentConfig(params: {
     params.config.agent = {
       ...agentConfig,
       ...Object.fromEntries(
-        Object.entries(builtinAgents).filter(([key]) => key !== "sisyphus"),
+        Object.entries(builtinAgents).filter(([key]) => key !== "sisyphus" && key !== "hephaestus"),
       ),
       ...filterDisabledAgents(filteredUserAgents),
       ...filterDisabledAgents(filteredProjectAgents),