llm: return concrete client types from provider constructors

Follow the Go idiom "return concrete types, accept interfaces": the
provider constructors newOpenAI, newAnthropic, newOpenRouter, newOllama
and their *WithTimeout variants now return their concrete *Client value
types instead of the Client interface. The provider factories registered
in the registry still return Client, so NewFromConfig and the registry
keep working unchanged.

Updated comments to explain the reasoning, dropped the now-redundant
type assertions in tests, and switched the anthropic Streamer-capability
tests to assert via an explicit Client interface value.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 9 insertions, 9 deletions

diff --git a/internal/llm/openai_http_test.go b/internal/llm/openai_http_test.go
index d0fc828..400ac18 100644
--- a/internal/llm/openai_http_test.go
+++ b/internal/llm/openai_http_test.go
@@ -23,7 +23,7 @@ func TestOpenAI_Chat_Success(t *testing.T) {
 		_ = json.NewEncoder(w).Encode(map[string]any{"choices": []map[string]any{{"index": 0, "message": map[string]string{"role": "assistant", "content": "OK"}}}})
 	}))
 	defer srv.Close()
-	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2)).(openAIClient)
+	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2))
 	c.httpClient = srv.Client()
 	out, err := c.Chat(context.Background(), []Message{{Role: "user", Content: "hi"}})
 	if err != nil || out != "OK" {
@@ -32,7 +32,7 @@ func TestOpenAI_Chat_Success(t *testing.T) {
 }
 
 func TestOpenAI_Chat_MissingKey(t *testing.T) {
-	c := newOpenAI("http://x", "g", "", f64p(0.2)).(openAIClient)
+	c := newOpenAI("http://x", "g", "", f64p(0.2))
 	if _, err := c.Chat(context.Background(), []Message{{Role: "user", Content: "hi"}}); err == nil {
 		t.Fatalf("expected error for missing key")
 	}
@@ -49,7 +49,7 @@ func TestOpenAI_ChatStream_SSE(t *testing.T) {
 		_, _ = io.WriteString(w, "data: [DONE]\n")
 	}))
 	defer srv.Close()
-	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2)).(openAIClient)
+	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2))
 	c.httpClient = srv.Client()
 	var got string
 	err := c.ChatStream(context.Background(), []Message{{Role: "user", Content: "hi"}}, func(s string) { got += s })
@@ -75,7 +75,7 @@ func TestOpenAI_ChatStream_SSE_ErrorChunk(t *testing.T) {
 		_, _ = io.WriteString(w, "data: [DONE]\n")
 	}))
 	defer srv.Close()
-	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2)).(openAIClient)
+	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2))
 	c.httpClient = srv.Client()
 	var got string
 	if err := c.ChatStream(context.Background(), []Message{{Role: "user", Content: "hi"}}, func(s string) { got += s }); err == nil {
@@ -91,7 +91,7 @@ func TestOpenAI_Chat_NoChoices_Error(t *testing.T) {
 		_ = json.NewEncoder(w).Encode(map[string]any{"choices": []any{}})
 	}))
 	defer srv.Close()
-	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2)).(openAIClient)
+	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2))
 	c.httpClient = srv.Client()
 	if _, err := c.Chat(context.Background(), []Message{{Role: "user", Content: "hi"}}); err == nil {
 		t.Fatalf("expected error when choices empty")
@@ -108,7 +108,7 @@ func TestOpenAI_ChatStream_SSE_EmptyDelta_NoError(t *testing.T) {
 		_, _ = io.WriteString(w, "data: [DONE]\\n")
 	}))
 	defer srv.Close()
-	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2)).(openAIClient)
+	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2))
 	c.httpClient = srv.Client()
 	var got string
 	if err := c.ChatStream(context.Background(), []Message{{Role: "user", Content: "hi"}}, func(s string) { got += s }); err != nil {
@@ -129,7 +129,7 @@ func TestOpenAI_Chat_DecodeError_StatusOK(t *testing.T) {
 		_, _ = io.WriteString(w, "{invalid")
 	}))
 	defer srv.Close()
-	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2)).(openAIClient)
+	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2))
 	c.httpClient = srv.Client()
 	if _, err := c.Chat(context.Background(), []Message{{Role: "user", Content: "hi"}}); err == nil {
 		t.Fatalf("expected decode error for invalid JSON body")
@@ -150,7 +150,7 @@ func TestOpenAI_Chat_MultiChoiceAndErrorBody(t *testing.T) {
 		})
 	}))
 	defer srv.Close()
-	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2)).(openAIClient)
+	c := newOpenAI(srv.URL, "g", "KEY", f64p(0.2))
 	c.httpClient = srv.Client()
 	out, err := c.Chat(context.Background(), []Message{{Role: "user", Content: "hi"}})
 	if err != nil || out != "FIRST" {
@@ -163,7 +163,7 @@ func TestOpenAI_Chat_MultiChoiceAndErrorBody(t *testing.T) {
 		_ = json.NewEncoder(w).Encode(map[string]any{"error": map[string]any{"message": "bad", "type": "invalid"}})
 	}))
 	defer srv2.Close()
-	c2 := newOpenAI(srv2.URL, "g", "KEY", f64p(0.2)).(openAIClient)
+	c2 := newOpenAI(srv2.URL, "g", "KEY", f64p(0.2))
 	c2.httpClient = srv2.Client()
 	if _, err := c2.Chat(context.Background(), []Message{{Role: "user", Content: "hi"}}); err == nil {
 		t.Fatalf("expected error from non-2xx with error body")