feat(agent): add external MCP client support

Reuse OpenCode 2 HTTP/stdio clients with per-session read-only grants,
native approval and sanitized owner-scoped MCP status. Narrow the
environment inherited by trusted local MCP processes.

Validated in an isolated checkout with bun run check and 20 focused tests.

.opencode/plugins/tjwater-tools.ts

@@ -10,6 +10,7 @@ import { Plugin, Rpc } from "@opencode/plugin";
 import { z } from "zod";
 import { resolve } from "node:path";
 import { registerSessionSandbox } from "../session-sandbox.js";
+import { registerMcpPolicy } from "../mcp-policy.js";
 
 import add_task_human_evidence from "../tools/add_task_human_evidence.js";
 import clear_scada_analysis from "../tools/clear_scada_analysis.js";
@@ -99,6 +100,7 @@ export default Plugin.define({
         },
       });
     });
+    const mcpReport = await registerMcpPolicy(ctx);
     await ctx.rpc.register(Rpc.define({
       id: "tjwater.tools",
       methods: {
@@ -106,9 +108,21 @@ export default Plugin.define({
           input: z.object({}),
           output: z.array(z.object({ id: z.string(), direct: z.boolean(), sandboxed: z.boolean(), workspaceRoot: z.string().optional() })),
         },
+        mcp: {
+          input: z.object({}),
+          output: z.object({
+            configuration_errors: z.array(z.string()),
+            servers: z.array(z.object({
+              name: z.string(), type: z.enum(["local", "remote"]),
+              status: z.enum(["connected", "pending", "disabled", "failed", "needs_auth"]),
+              configured_protocol: z.enum(["legacy", "auto", "2026-07-28"]), tools: z.array(z.string()),
+            })),
+          }),
+        },
       },
       events: {},
     }), {
+      mcp: mcpReport,
       list: async () => (await ctx.tool.list()).map((tool) => ({
         id: tool.id,
         direct: tool.options?.codemode === false,