fix(extension): 完成MCP命令目标并收紧Schema边界

backend/extensions/fixtures/mcp-echo/commands.yaml

@@ -0,0 +1,20 @@
+commands:
+  - command_id: mcp-fixture.notify
+    title: MCP 通知
+    description: 通过隔离 MCP Host 返回宿主白名单通知 effect。
+    icon: bolt
+    locations:
+      - command_palette
+    when:
+      - editor.has_selection
+    context:
+      - selection
+    secrets:
+      - api_key
+    mcp_tool: mcp-fixture.command
+    parameters:
+      type: object
+      properties:
+        message:
+          type: string
+      additionalProperties: false

backend/extensions/fixtures/mcp-echo/plugin.yaml

@@ -1,9 +1,10 @@
 id: mcp-fixture
 name: MCP Fixture
 version: 1.0.0
-description: 阶段 C 离线联调 Fixture，覆盖 MCP Tool 生命周期与错误边界。
+description: 阶段 C/D 离线联调 Fixture，覆盖 MCP Tool、Command 与错误边界。
 permissions:
   - notes.read
+  - secrets.use
 contributes:
   tools:
     - mcp-fixture.echo
@@ -12,6 +13,10 @@ contributes:
     - mcp-fixture.large
     - mcp-fixture.environment
     - mcp-fixture.exit
+  commands:
+    - mcp-fixture.notify
+  settings_sections:
+    - mcp-fixture.general
 backend:
   type: mcp
   transport: stdio

backend/extensions/fixtures/mcp-echo/server.py

@@ -54,6 +54,11 @@ TOOLS = {
     "large": tool("large", "Return a result larger than the host limit."),
     "environment": tool("environment", "Report whether host secrets leaked into the process."),
     "exit": tool("exit", "Terminate the fixture process."),
+    "command": tool(
+        "command",
+        "Execute a NotesAgent Plugin Command envelope.",
+        {"_notesagent": {"type": "object"}},
+    ),
 }
 # suffix 是可选字段，用于验证 Host 不会把缺省值擅自补成 null。
 TOOLS["echo"]["inputSchema"]["required"] = ["text"]
@@ -62,6 +67,28 @@ TOOLS["echo"]["inputSchema"]["required"] = ["text"]
 def call_tool(request_id: int, params: dict[str, Any]) -> None:
     name = params.get("name")
     arguments = params.get("arguments") or {}
+    if name == "command":
+        envelope = arguments.get("_notesagent") or {}
+        command_arguments = envelope.get("arguments") or {}
+        context = envelope.get("context") or {}
+        secrets = envelope.get("secrets") or {}
+        message = command_arguments.get("message") or context.get("selection") or ""
+        respond(
+            request_id,
+            {
+                "content": [{"type": "text", "text": "command completed"}],
+                "structuredContent": {
+                    "type": "notification",
+                    "payload": {
+                        "level": "success",
+                        "message": str(message),
+                        "secret_configured": isinstance(secrets.get("api_key"), str),
+                    },
+                },
+                "isError": False,
+            },
+        )
+        return
     if name == "echo":
         text = str(arguments.get("text", ""))
         structured_content = {"echo": text}
@@ -183,7 +210,14 @@ def main() -> None:
             elif params.get("cursor") == "page-2":
                 respond(
                     request_id,
-                    {"tools": [TOOLS["large"], TOOLS["environment"], TOOLS["exit"]]},
+                    {
+                        "tools": [
+                            TOOLS["large"],
+                            TOOLS["environment"],
+                            TOOLS["exit"],
+                            TOOLS["command"],
+                        ]
+                    },
                 )
             else:
                 respond(

backend/extensions/fixtures/mcp-echo/settings.yaml

@@ -0,0 +1,7 @@
+section_id: mcp-fixture.general
+schema_version: 1
+fields:
+  - key: api_key
+    label: Fixture API Key
+    type: secret
+    required: true