fix(model): DeepSeek 推理参数语义反转 + thinking 开关真发（按官方文档核对结果）

依据 DevDocs/design/04 §3.2「官方核对后的修正」9 条 + 本地 DevDocs/reference/deepseek/facts-for-cyrene.md（官方原句/URL）。
- 🔴 reasoning_effort 白名单改为官方集合 [none, low, high, max] + 别名映射(minimal→low, medium→high, xhigh→high, ultra→max)；**删除就近降级**，非法值一律丢弃+WARN。此前 none(关思考) 被降级成 low(开思考) 属语义反转
- 🔴 DeepSeek thinking 开关真发顶层 {"thinking":{"type":"enabled|disabled"}}（官方默认 enabled，不传≠关）；此前只打 WARN 导致 mode:off 静默无效
- DeepSeek 的 /anthropic 端点忽略 budget_tokens → 不再对其抬 max_tokens（会误导预算/日志），改为按官方用 output_config.effort
- 注释纠正：penalty 属接口级 deprecated（非仅思考模式）；top_p 仅思考模式生效且下限 0.95（不加该字段）
- tool_choice 雷登记：思考模式下 required/指定 tool 会 400（思考默认开）
- 旧模型名清理（deepseek-chat/reasoner 已于 2026-07-24 停用）
- 请求体级测试 + 变异验证（把 none 改回 low / 把 thinking 改回只 WARN → 对应断言 FAIL）

internal/runtime/model/reasoning_test.go

@@ -175,28 +175,29 @@ func TestOpenAIChat_ReasoningEffortPassthrough(t *testing.T) {
 	}
 }
 
-// TestOpenAIChat_ReasoningEffortDowngradedForDeepSeek asserts a tier the vendor
-// does not accept (DeepSeek allows only low/high/max) is rounded down to the
-// nearest allowed tier and reported, never forwarded as-is.
-func TestOpenAIChat_ReasoningEffortDowngradedForDeepSeek(t *testing.T) {
+// TestOpenAIChat_ReasoningEffortAliasMappedForDeepSeek asserts a DeepSeek
+// compatibility alias is normalized to the tier the service applies (medium →
+// high per the official mapping table) and reported, never graded down to a
+// weaker tier of our own choosing.
+func TestOpenAIChat_ReasoningEffortAliasMappedForDeepSeek(t *testing.T) {
 	t.Parallel()
 	ch := make(chan capturedRequest, 1)
 	srv := newCompletionServer(t, http.StatusOK, "application/json", okCompletion, ch)
 	log, buf := captureLog()
-	ad := NewOpenAIChat(config.LLMConfig{BaseURL: srv.URL, Model: "deepseek-chat"}, WithOpenAILogger(log))
+	ad := NewOpenAIChat(config.LLMConfig{BaseURL: srv.URL, Model: "deepseek-flash"}, WithOpenAILogger(log))
 
 	if _, err := ad.Chat(context.Background(), Request{
-		Model:           "deepseek-chat",
+		Model:           "deepseek-flash",
 		Messages:        []Message{TextMessage(RoleUser, "hi")},
 		ReasoningEffort: "medium",
 	}, Options{}); err != nil {
 		t.Fatalf("Chat error: %v", err)
 	}
-	if got := (<-ch).body["reasoning_effort"]; got != "low" {
-		t.Fatalf("body.reasoning_effort = %v, want the downgraded low", got)
+	if got := (<-ch).body["reasoning_effort"]; got != "high" {
+		t.Fatalf("body.reasoning_effort = %v, want the officially mapped high", got)
 	}
 	rec := buf.String()
-	for _, want := range []string{"level=WARN", "reasoning_effort", "deepseek", "medium", "low"} {
+	for _, want := range []string{"level=WARN", "reasoning_effort", "deepseek", "medium", "high"} {
 		if !strings.Contains(rec, want) {
 			t.Errorf("log %q missing %q", rec, want)
 		}
@@ -346,7 +347,7 @@ func TestReasoningVendorFor_Classification(t *testing.T) {
 		baseURL string
 		want    reasoningVendor
 	}{
-		{model: "deepseek-reasoner", want: vendorDeepSeek},
+		{model: "deepseek-v4-pro", want: vendorDeepSeek},
 		{model: "Qwen3-Max", want: vendorQwen},
 		{model: "gpt-4o", want: vendorOpenAI},
 		{model: "o3-mini", want: vendorOpenAI},