feat(providers): add four OpenAI-compatible aggregator providers (dahl, atria, agnes, bai)

Adds Dahl Inference, Atria Dawn, Agnes AI, and B.AI following the existing
registry pattern. Each uses DefaultExecutor with no custom translator needed.

open-sse/providers/registry/dahl.js

@@ -0,0 +1,35 @@
+export default {
+  id: "dahl",
+  priority: 120,
+  alias: "dahl",
+  aliases: [
+    "dahl-inference",
+  ],
+  uiAlias: "dahl",
+  display: {
+    name: "Dahl Inference",
+    icon: "hub",
+    color: "#1E40AF",
+    textIcon: "DH",
+    website: "https://dahl.global",
+    notice: {
+      text: "OpenAI-compatible Gonka inference node. Small, fixed catalogue (GLM-5.3-Flash, DeepSeek-V4-Flash, MiniMax-M2.7) at a flat per-token rate.",
+      apiKeyUrl: "https://dahl.global/dashboard",
+    },
+  },
+  category: "apikey",
+  authType: "apikey",
+  transport: {
+    baseUrl: "https://inference.dahl.global/v1/chat/completions",
+    validateUrl: "https://inference.dahl.global/v1/models",
+  },
+  // The live catalogue is public (no auth), so modelsFetcher works without a key
+  // and the ids below are a convenience seed rather than an exhaustive list.
+  models: [
+    { id: "zai-org/GLM-5.3-Flash", name: "GLM-5.3 Flash" },
+    { id: "deepseek-ai/DeepSeek-V4-Flash-0731", name: "DeepSeek V4 Flash 0731" },
+    { id: "MiniMaxAI/MiniMax-M2.7", name: "MiniMax M2.7" },
+  ],
+  modelsFetcher: { url: "https://inference.dahl.global/v1/models", type: "openai" },
+  passthroughModels: true,
+};