feat: 将插件 stdin 协议定为 v1，并按声明注入凭据

进程外插件改为只读环境变量和自身配置，避免读宿主 appsettings；宿主按 plugin.json 声明注入 LLM / OpenWeather 等凭据。

MAF1.Core/PluginContract/PluginManifest.cs

@@ -12,6 +12,10 @@ public sealed class PluginManifest
     public string Name { get; set; } = "";
     public string Description { get; set; } = "";
     public string Version { get; set; } = "1.0.0";
+
+    /// <summary>stdin/stdout 协议主版本。缺省或 0 视为 1。宿主拒绝大于 <see cref="PluginProtocol.Current"/> 的值。</summary>
+    public int ProtocolVersion { get; set; }
+
     public PluginLaunch Launch { get; set; } = new();
     public int TimeoutSeconds { get; set; }
     public Dictionary<string, string> Env { get; set; } = new(StringComparer.OrdinalIgnoreCase);
@@ -45,9 +49,51 @@ public sealed class PluginCredentialNeed
     public string Description { get; set; } = "";
 }
 
+/// <summary>stdin/stdout JSON 协议版本。缺省字段按 1 处理，便于旧 plugin.json 继续用。</summary>
+public static class PluginProtocol
+{
+    public const int Current = 1;
+
+    public static int Normalize(int version) => version <= 0 ? 1 : version;
+
+    public static bool IsSupported(int version)
+    {
+        int normalized = Normalize(version);
+        return normalized >= 1 && normalized <= Current;
+    }
+}
+
+/// <summary>凭据 type 约定。宿主按类型注入环境变量，未知类型只传 stdin Extra。</summary>
+public static class PluginCredentialTypes
+{
+    public const string OpenAiCompatible = "openai-compatible";
+    public const string Llm = "llm";
+    public const string OpenWeather = "openweather";
+
+    public static bool IsLlm(string? type)
+        => type is OpenAiCompatible or Llm
+            || string.Equals(type, "openai-compatible", StringComparison.OrdinalIgnoreCase)
+            || string.Equals(type, "llm", StringComparison.OrdinalIgnoreCase);
+
+    public static bool IsOpenWeather(string? type)
+        => string.Equals(type, OpenWeather, StringComparison.OrdinalIgnoreCase);
+
+    public static bool Matches(string? declaredType, string? recordType)
+    {
+        if (IsLlm(declaredType) && IsLlm(recordType))
+        {
+            return true;
+        }
+
+        return string.Equals(declaredType, recordType, StringComparison.OrdinalIgnoreCase);
+    }
+}
+
 /// <summary>宿主写入插件 stdin 的整包请求：业务输入 + 凭据。</summary>
 public sealed class PluginRequest
 {
+    public int ProtocolVersion { get; set; } = PluginProtocol.Current;
+
     public Dictionary<string, object?> Inputs { get; set; } = new(StringComparer.OrdinalIgnoreCase);
 
     [JsonPropertyName("credentials")]