feat(FN-3332): add droid runtime plugin with event bridge and process manag

The merge delivers a new `fusion-plugin-droid-runtime` plugin providing a full MCP server and runtime adapter for droid-based agents, with event bridging, process management, tool mapping, and a prompt builder. It also adds agent delegation and org hierarchy tools to the pi extension, while fixing a

Fusion-Task-Id: FN-3332

plugins/fusion-plugin-droid-runtime/src/mcp-schema-server.cjs

@@ -0,0 +1,49 @@
+#!/usr/bin/env node
+// Schema-only MCP server. Reads tool schemas from a JSON file.
+// Only implements initialize + tools/list. tools/call is never reached
+// because the parent process kills the Claude subprocess at message_stop
+// before tool execution (break-early pattern).
+"use strict";
+
+const fs = require("fs");
+const readline = require("readline");
+
+const schemaPath = process.argv[2];
+if (!schemaPath) {
+  process.exit(1);
+}
+
+let tools = [];
+try {
+  tools = JSON.parse(fs.readFileSync(schemaPath, "utf-8"));
+} catch {
+  process.exit(1);
+}
+
+const rl = readline.createInterface({ input: process.stdin });
+rl.on("line", (line) => {
+  let msg;
+  try {
+    msg = JSON.parse(line);
+  } catch {
+    return;
+  }
+
+  if (msg.method === "initialize") {
+    const resp = {
+      jsonrpc: "2.0",
+      id: msg.id,
+      result: {
+        protocolVersion: "2024-11-05",
+        capabilities: { tools: {} },
+        serverInfo: { name: "custom-tools", version: "1.0.0" },
+      },
+    };
+    process.stdout.write(JSON.stringify(resp) + "\n");
+  } else if (msg.method === "tools/list") {
+    const resp = { jsonrpc: "2.0", id: msg.id, result: { tools } };
+    process.stdout.write(JSON.stringify(resp) + "\n");
+  }
+  // notifications/initialized: no response needed (notification)
+  // tools/call: never reached (break-early kills subprocess first)
+});