fix(provider): clarify local 502 recovery hints

tests/providers/test_custom_provider.py

@@ -4,6 +4,7 @@ from types import SimpleNamespace
 from unittest.mock import patch
 
 from nanobot.providers.openai_compat_provider import OpenAICompatProvider
+from nanobot.providers.registry import find_by_name
 
 
 def test_custom_provider_parse_handles_empty_choices() -> None:
@@ -53,3 +54,16 @@ def test_custom_provider_parse_chunks_accepts_plain_text_chunks() -> None:
 
     assert result.finish_reason == "stop"
     assert result.content == "hello world"
+
+
+def test_local_provider_502_error_includes_reachability_hint() -> None:
+    spec = find_by_name("ollama")
+    with patch("nanobot.providers.openai_compat_provider.AsyncOpenAI"):
+        provider = OpenAICompatProvider(api_base="http://localhost:11434/v1", spec=spec)
+
+    result = provider._handle_error(Exception("Error code: 502"))
+
+    assert result.finish_reason == "error"
+    assert "local model endpoint" in result.content
+    assert "http://localhost:11434/v1" in result.content
+    assert "proxy/tunnel" in result.content