fix: bundle config/recursion/missing-key fixes

- dataflows/config: deepcopy + one-level dict merge so a partial
  set_config doesn't clobber sibling defaults
- graph: thread max_recur_limit from config to Propagator
- openai_client: name the missing env var in the API-key error

#788 #764 #680

tests/conftest.py

@@ -19,6 +19,8 @@ _API_KEY_ENV_VARS = (
     "DEEPSEEK_API_KEY",
     "DASHSCOPE_API_KEY",
     "ZHIPU_API_KEY",
+    "MINIMAX_API_KEY",
+    "MINIMAX_CN_API_KEY",
     "OPENROUTER_API_KEY",
     "AZURE_OPENAI_API_KEY",
     "ALPHA_VANTAGE_API_KEY",