feat: kimi (Moonshot AI) built-in provider (ADR-0026)

Add a first-class `kimi` provider and `kimi://` DSN scheme for Moonshot AI's
OpenAI-compatible Chat Completions API. Both reuse provider/openai (no new
client, mirroring llama-swap's chat path). Default endpoint is the
international host; the China endpoint is reachable via a kimi:// LLM_* DSN.

- Credential is KIMI_API_KEY, read through the registry's injected envLookup
  so it stays hermetically testable. WithAPIKey is passed unconditionally so
  an unset KIMI_API_KEY can never fall through to the openai client's
  OPENAI_API_KEY default.
- New openai.WithAPIKeyName option customizes the missing-key error hint
  (default OPENAI_API_KEY); kimi names KIMI_API_KEY.
- Hermetic tests: built-in base URL + bearer, missing-key hint names
  KIMI_API_KEY with no OPENAI fallthrough and no network hit, kimi:// scheme
  round-trips against the China host.
- Docs in sync: README built-in table + DSN scheme list + support matrix,
  .env.example, env.go DSN doc, ADR-0026 (+ index, backfilling 0024/0025),
  progress.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>

builtin_kimi_test.go

@@ -0,0 +1,138 @@
+package majordomo
+
+import (
+	"context"
+	"errors"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+
+	"gitea.stevedudenhoeffer.com/steve/majordomo/llm"
+)
+
+// kimiResponse is a minimal valid Chat Completions body so Generate returns a
+// non-empty response (an empty one would trigger failover, not a clean pass).
+const kimiResponse = `{"id":"c1","object":"chat.completion","choices":[` +
+	`{"index":0,"message":{"role":"assistant","content":"ok"},"finish_reason":"stop"}]}`
+
+// captureRT records the last request and returns a canned response without
+// touching the network, so these tests stay hermetic while still exercising
+// the real openai client the kimi built-in reuses (base URL + auth header).
+type captureRT struct {
+	req  *http.Request
+	body string
+}
+
+func (c *captureRT) RoundTrip(r *http.Request) (*http.Response, error) {
+	c.req = r
+	return &http.Response{
+		StatusCode: http.StatusOK,
+		Body:       io.NopCloser(strings.NewReader(c.body)),
+		Header:     make(http.Header),
+		Request:    r,
+	}, nil
+}
+
+// TestKimiBuiltin: the built-in "kimi" provider resolves in Parse, targets
+// Moonshot's default endpoint, and authenticates with KIMI_API_KEY.
+func TestKimiBuiltin(t *testing.T) {
+	rt := &captureRT{body: kimiResponse}
+	r := newTestRegistry(t,
+		WithEnvLookup(func(k string) string {
+			if k == "KIMI_API_KEY" {
+				return "kimi-secret"
+			}
+			return ""
+		}),
+		WithHTTPClient(&http.Client{Transport: rt}),
+	)
+
+	if p, ok := r.Provider(ProviderKimi); !ok {
+		t.Fatal("built-in kimi provider not registered")
+	} else if p.Name() != ProviderKimi {
+		t.Errorf("name = %q, want %q", p.Name(), ProviderKimi)
+	}
+
+	m, err := r.Parse("kimi/kimi-k2-0711-preview")
+	if err != nil {
+		t.Fatalf("Parse: %v", err)
+	}
+	if got := targetsOf(t, m); len(got) != 1 || got[0] != "kimi/kimi-k2-0711-preview" {
+		t.Fatalf("targets = %v", got)
+	}
+
+	if _, err := m.Generate(context.Background(), llm.Request{Messages: []llm.Message{llm.UserText("hi")}}); err != nil {
+		t.Fatalf("Generate: %v", err)
+	}
+	if rt.req == nil {
+		t.Fatal("no request captured")
+	}
+	if want := "https://api.moonshot.ai/v1/chat/completions"; rt.req.URL.String() != want {
+		t.Errorf("URL = %q, want %q", rt.req.URL.String(), want)
+	}
+	if want := "Bearer kimi-secret"; rt.req.Header.Get("Authorization") != want {
+		t.Errorf("Authorization = %q, want %q", rt.req.Header.Get("Authorization"), want)
+	}
+}
+
+// TestKimiBuiltinMissingKey: with no KIMI_API_KEY the built-in fails fast with a
+// synthetic 401 whose hint names KIMI_API_KEY — never OPENAI_API_KEY (proving
+// the credential does not fall through to the openai client's default), and
+// without hitting the network.
+func TestKimiBuiltinMissingKey(t *testing.T) {
+	rt := &captureRT{body: kimiResponse}
+	r := newTestRegistry(t, WithHTTPClient(&http.Client{Transport: rt}))
+
+	m, err := r.Parse("kimi/kimi-k2-0711-preview")
+	if err != nil {
+		t.Fatalf("Parse: %v", err)
+	}
+	_, err = m.Generate(context.Background(), llm.Request{Messages: []llm.Message{llm.UserText("hi")}})
+	apiErr, ok := errors.AsType[*llm.APIError](err)
+	if !ok {
+		t.Fatalf("err = %v (%T), want *llm.APIError", err, err)
+	}
+	if apiErr.Status != http.StatusUnauthorized || apiErr.Code != "missing_api_key" {
+		t.Errorf("Status/Code = %d/%q, want 401/missing_api_key", apiErr.Status, apiErr.Code)
+	}
+	if !strings.Contains(apiErr.Message, "KIMI_API_KEY") {
+		t.Errorf("message = %q, want it to name KIMI_API_KEY", apiErr.Message)
+	}
+	if strings.Contains(apiErr.Message, "OPENAI_API_KEY") {
+		t.Errorf("message = %q, must not name OPENAI_API_KEY", apiErr.Message)
+	}
+	if rt.req != nil {
+		t.Error("network was hit despite missing key")
+	}
+}
+
+// TestKimiScheme: a kimi:// LLM_* DSN defines a named provider on any Moonshot
+// host (here the China endpoint) that is first-class in Parse and carries the
+// DSN token as its bearer credential.
+func TestKimiScheme(t *testing.T) {
+	rt := &captureRT{body: kimiResponse}
+	r := newTestRegistry(t, WithHTTPClient(&http.Client{Transport: rt}))
+	if err := r.LoadEnv(map[string]string{
+		"LLM_KCN": "kimi://[email protected]/v1",
+	}); err != nil {
+		t.Fatalf("LoadEnv: %v", err)
+	}
+
+	m, err := r.Parse("kcn/moonshot-v1-8k")
+	if err != nil {
+		t.Fatalf("Parse: %v", err)
+	}
+	if _, err := m.Generate(context.Background(), llm.Request{Messages: []llm.Message{llm.UserText("hi")}}); err != nil {
+		t.Fatalf("Generate: %v", err)
+	}
+	if rt.req == nil {
+		t.Fatal("no request captured")
+	}
+	if want := "https://api.moonshot.cn/v1/chat/completions"; rt.req.URL.String() != want {
+		t.Errorf("URL = %q, want %q", rt.req.URL.String(), want)
+	}
+	if want := "Bearer tok"; rt.req.Header.Get("Authorization") != want {
+		t.Errorf("Authorization = %q, want %q", rt.req.Header.Get("Authorization"), want)
+	}
+}