feat(mcp): P0 只读 MCP tool runtime + opsxdb-mcp stdio

- aitools 共用 runtime：list/describe/schema/query/redis（纯只读，无写确认）
- 白名单 ~/.opsxdb/mcp.json；审计 mcp-audit.jsonl；复用 danger.go
- 桌面 connections 双写 ~/.opsxdb/connections.json（ox1. 解码）
- Cursor 配置示例与任务书验收勾选更新；写操作与 Agent UI 留 P1

server/cmd/opsxdb-mcp/main.go

@@ -0,0 +1,109 @@
+// opsxdb-mcp：stdio MCP Server，暴露只读数据库工具（P0）。 // Logan.Li
+//
+// 配置：
+//   ~/.opsxdb/mcp.json          — allowed_connection_ids；mode（P0 执行层强制只读）
+//   ~/.opsxdb/connections.json  — 桌面双写的连接列表（密码 ox1. 混淆）
+//   ~/.opsxdb/logs/mcp-audit.jsonl
+//
+// Cursor 示例见 docs/mcp-cursor.example.json
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/mark3labs/mcp-go/mcp"
+	"github.com/mark3labs/mcp-go/server"
+
+	"opsxdb/server/internal/aitools"
+)
+
+func main() {
+	rt, err := aitools.DefaultRuntime()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "opsxdb-mcp: load policy: %v\n", err)
+		os.Exit(1)
+	}
+
+	s := server.NewMCPServer(
+		"opsxdb",
+		"0.1.0",
+		server.WithToolCapabilities(true),
+	)
+
+	register := func(name, desc string, props map[string]any, required []string) {
+		schema := map[string]any{
+			"type":       "object",
+			"properties": props,
+		}
+		if len(required) > 0 {
+			schema["required"] = required
+		}
+		raw, _ := json.Marshal(schema)
+		t := mcp.NewToolWithRawSchema(name, desc, raw)
+		toolName := name
+		s.AddTool(t, func(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+			args := req.GetArguments()
+			out, err := rt.Call(ctx, toolName, args)
+			if err != nil {
+				return mcp.NewToolResultError(err.Error()), nil
+			}
+			return mcp.NewToolResultText(aitools.ResultJSON(out)), nil
+		})
+	}
+
+	connID := map[string]any{"type": "string", "description": "Saved connection id from opsxdb_list_connections"}
+	database := map[string]any{"type": "string", "description": "Database / schema / Redis DB index"}
+
+	register(aitools.ToolListConnections,
+		"List whitelisted OpsxDB connections (id/name/driver/host/port/database; never passwords).",
+		map[string]any{}, nil)
+
+	register(aitools.ToolListDatabases,
+		"List databases for a connection.",
+		map[string]any{"connection_id": connID}, []string{"connection_id"})
+
+	register(aitools.ToolListTables,
+		"List tables/views (or engine equivalents) in a database.",
+		map[string]any{"connection_id": connID, "database": database}, []string{"connection_id"})
+
+	register(aitools.ToolDescribeTable,
+		"Describe columns and metadata for a table.",
+		map[string]any{
+			"connection_id": connID,
+			"database":      database,
+			"table":         map[string]any{"type": "string", "description": "Table name"},
+		}, []string{"connection_id", "table"})
+
+	register(aitools.ToolGetSchemaContext,
+		"Compact schema text for LLM context (capped ~4k chars).",
+		map[string]any{
+			"connection_id": connID,
+			"database":      database,
+			"max_tables":    map[string]any{"type": "integer", "description": "Max tables to include (default 40)"},
+		}, []string{"connection_id"})
+
+	register(aitools.ToolExecuteQuery,
+		"Execute a READ-ONLY SQL query (SELECT/SHOW/EXPLAIN/WITH…SELECT). Writes and DDL are rejected in P0. Default limit 100, max 500.",
+		map[string]any{
+			"connection_id": connID,
+			"sql":           map[string]any{"type": "string", "description": "Read-only SQL"},
+			"database":      database,
+			"limit":         map[string]any{"type": "integer", "description": "Row limit (default 100, max 500)"},
+		}, []string{"connection_id", "sql"})
+
+	register(aitools.ToolExecuteRedisCommand,
+		"Execute a READ-ONLY Redis command (GET/SCAN/TYPE/TTL/…). FLUSH*/KEYS and writes are rejected in P0.",
+		map[string]any{
+			"connection_id": connID,
+			"command":       map[string]any{"type": "string", "description": "Single Redis command line"},
+			"database":      database,
+		}, []string{"connection_id", "command"})
+
+	if err := server.ServeStdio(s); err != nil {
+		fmt.Fprintf(os.Stderr, "opsxdb-mcp: %v\n", err)
+		os.Exit(1)
+	}
+}