docs: RULES.md lists only the RPC endpoint as contacted by default (closes #755)

The External Communication checklist named CoinDesk and Blockscout as
always contacted. USD prices now come from Chainlink feeds read through
the RPC endpoint, and Blockscout and Etherscan stay off until the user
turns them on. Both lines now say so, in the wording sneak approved on
the issue.

Model: opus-5-5

RULES.md

@@ -22,10 +22,12 @@ contradicts either, the originals govern.
 
 ## External Communication
 
-- [ ] Extension contacts exactly three external services: configured RPC
+- [ ] Until the user changes a setting, the extension contacts only the
-      endpoint, CoinDesk price API, and Blockscout block-explorer API
+      configured RPC endpoint
 - [ ] No analytics, telemetry, or tracking
-- [ ] No user-specific data sent except to the configured RPC endpoint
+- [ ] No user-specific data sent except to the configured RPC endpoint, unless
+      the user turns on "Use Blockscout" or "Check recipients on Etherscan",
+      both off by default
 - [ ] No Infura/Alchemy hard dependency
 - [ ] No backend servers operated by the developer
 - [ ] RPC endpoint is user-configurable (defaults to publicnode.com)

eslint.config.js

@@ -135,9 +135,14 @@ module.exports = [
         },
     },
 
-    // Unit tests, and the helpers they require: jest on node.
+    // Unit tests, the helpers they require, and the test files they hand to
+    // jest: jest on node.
     {
-        files: ["tests/**/*.test.js", "tests/support/**/*.js"],
+        files: [
+            "tests/**/*.test.js",
+            "tests/support/**/*.js",
+            "tests/fixtures/**/*.js",
+        ],
         languageOptions: {
             ...commonjs,
             globals: { ...globals.node, ...globals.jest },

package.json

@@ -16,7 +16,8 @@
     "jest": {
         "setupFiles": [
             "<rootDir>/tests/support/navigatorLocks.js"
-        ]
+        ],
+        "workerIdleMemoryLimit": "200MB"
     },
     "devDependencies": {
         "@eslint/js": "10.0.1",

tests/fixtures/leavesIntervalRunning.js

@@ -0,0 +1,7 @@
+// A test file that starts an interval and never clears it.
+// tests/jestRunner.test.js runs script/lib/jest.js on this file alone. The
+// name does not end in .test.js, so the normal run never picks it up.
+
+test("starts an interval and never clears it", () => {
+    setInterval(() => {}, 1000);
+});

tests/jestRunner.test.js

@@ -0,0 +1,29 @@
+// script/lib/jest.js, which package.json's test scripts run, fails a run in
+// which jest force-stopped a worker process because a test left an open
+// handle.
+
+const { spawnSync } = require("child_process");
+const path = require("path");
+
+const root = path.join(__dirname, "..");
+
+test("a test that leaves an interval running fails the run", () => {
+    // The memory limit in package.json makes jest run even this one file in a
+    // worker process. The interval keeps that worker from exiting, so jest
+    // force-stops it after the run.
+    const result = spawnSync(
+        process.execPath,
+        [
+            "script/lib/jest.js",
+            "--maxWorkers=1",
+            "--testMatch",
+            "<rootDir>/tests/fixtures/leavesIntervalRunning.js",
+        ],
+        { cwd: root, encoding: "utf8", timeout: 20000 },
+    );
+
+    expect(result.signal).toBeNull();
+    expect(result.status).toBe(1);
+    expect(result.stderr).toContain("1 passed");
+    expect(result.stderr).toContain("jest force-stopped a worker process");
+});