Let the gateway target non-OpenAI upstreams and allow client model passthrough

gateway_thinking_dialect overrides the URL-sniffed protocol dialect for a
reverse-proxied upstream (e.g. Ollama) whose URL carries no identifying
token; upstream_capabilities() uses the same effective dialect to stop
sending stream_options to upstreams that don't support it. gateway_allow_client_model
lets a client-requested model name through even with force-model on, for
an upstream that serves many models with no single stable alias.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XjW4qocnaJxhugUi5ca8Wo

tests/unit/services/openai_gateway/thinking.py

@@ -4,6 +4,7 @@ from devplacepy.services.openai_gateway.thinking import (
     apply_thinking,
     client_thinking_enabled,
     thinking_dialect,
+    upstream_capabilities,
 )
 
 
@@ -15,6 +16,38 @@ def test_dialect_from_upstream_url():
     assert thinking_dialect("https://unknown.example/v1/chat/completions") == "deepseek"
 
 
+def test_upstream_capabilities_openai_full_schema():
+    caps = upstream_capabilities("https://api.deepseek.com/chat/completions")
+    assert caps.dialect == "deepseek"
+    assert caps.supports_stream_options is True
+    assert caps.supports_stream_usage is True
+
+
+def test_upstream_capabilities_ollama_lacks_stream_options():
+    caps = upstream_capabilities("http://127.0.0.1:11434/api/chat")
+    assert caps.dialect == "ollama"
+    assert caps.supports_stream_options is False
+    assert caps.supports_stream_usage is False
+
+
+def test_upstream_capabilities_explicit_dialect_override():
+    caps = upstream_capabilities(
+        "https://ai.example.com/v1/chat/completions", dialect="ollama"
+    )
+    assert caps.dialect == "ollama"
+    assert caps.supports_stream_options is False
+
+
+def test_apply_thinking_respects_explicit_dialect_override():
+    without = apply_thinking({}, "https://ai.example.com/v1/chat/completions")
+    assert without["thinking"] == {"type": "disabled"}
+    with_override = apply_thinking(
+        {}, "https://ai.example.com/v1/chat/completions", dialect="ollama"
+    )
+    assert with_override["think"] is False
+    assert "thinking" not in with_override
+
+
 def test_client_intent_unspecified():
     assert client_thinking_enabled({}) is None
     assert client_thinking_enabled({"messages": []}) is None