test(harness): fake-pi-runtime mock for gate CI tests

harness/.pi/extensions/gate/__tests__/fake_pi_runtime.js

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+// fake_pi_runtime.js — minimal mock of the Pi extension runtime for gate tests.
+// Models Pi's NATIVE extension UI API (ctx.ui.select/confirm/input). There is NO
+// ctx.sendRaw in Pi; the gate awaits ctx.ui.* and the runtime routes the response.
+function createFakePi() {
+  const handlers = new Map();
+  const tools = new Map();
+  const ctx = {
+    hasUI: true,
+    cwd: "/tmp/fake-pi-session",
+    notifications: [],
+    uiCalls: [],
+    uiQueue: [],
+    ui: {
+      notify: async (message, level = "info") => ctx.notifications.push({ message, level }),
+      input: async (title, placeholder, opts) => { ctx.uiCalls.push({ method: "input", title, placeholder, opts }); return ctx.uiQueue.shift(); },
+      select: async (title, options, opts) => { ctx.uiCalls.push({ method: "select", title, options, opts }); return ctx.uiQueue.shift(); },
+      confirm: async (title, message, opts) => { ctx.uiCalls.push({ method: "confirm", title, message, opts }); return ctx.uiQueue.shift(); },
+    },
+  };
+  const pi = {
+    on: (event, handler) => {
+      if (!handlers.has(event)) handlers.set(event, []);
+      handlers.get(event).push(handler);
+    },
+    registerTool: (def, fn) => tools.set(def?.name ?? def, { def, fn }),
+    emit: async (event, payload) => {
+      let result;
+      for (const h of handlers.get(event) ?? []) result = await h(payload, ctx);
+      return result;
+    },
+  };
+  return { pi, ctx, tools, emit: pi.emit, enqueueUi: (v) => ctx.uiQueue.push(v) };
+}
+module.exports = { createFakePi };

harness/.pi/extensions/gate/__tests__/fake_pi_runtime.test.js

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+const test = require("node:test");
+const assert = require("node:assert");
+const { createFakePi } = require("./fake_pi_runtime.js");
+
+test("pi.on + emit invoca il handler e ne ritorna il valore", async () => {
+  const { pi } = createFakePi();
+  pi.on("tool_call", (e) => (e.toolName === "x" ? { block: true } : undefined));
+  assert.deepEqual(await pi.emit("tool_call", { toolName: "x" }), { block: true });
+  assert.equal(await pi.emit("tool_call", { toolName: "y" }), undefined);
+});
+
+test("ctx.ui.input registra la chiamata e ritorna il valore in coda (API nativa)", async () => {
+  const { ctx, enqueueUi } = createFakePi();
+  enqueueUi('{"id":"u1","choices":["a"]}');
+  const v = await ctx.ui.input("title-json", "");
+  assert.equal(v, '{"id":"u1","choices":["a"]}');
+  assert.equal(ctx.uiCalls[0].method, "input");
+  assert.equal(ctx.uiCalls[0].title, "title-json");
+});
+
+test("ctx.ui.input senza valore in coda ritorna undefined (modella cancel)", async () => {
+  const { ctx } = createFakePi();
+  assert.equal(await ctx.ui.input("t", ""), undefined);
+});