tabs: one window for every agent; inactive tabs take input; background off by defaultHEADmaster

Measured in Brave on 2026-11-14: an inactive tab takes trusted CDP clicks,
key presses, text and mouse moves, and Page.captureScreenshot renders it
live. Only mouseWheel hangs, waiting for a frame. The upstream guard that
refused input to every hidden page was wrong for inactive tabs, and it is
what made a window per session look necessary.

- New sessions' tabs open inactive in the user's last focused window, in
  the session's tab group; a window is created only when none is open.
- New groups start collapsed, unless their tab is the one showing, and
  expand when a tab in them is brought forward. Existing groups keep the
  user's setting.
- Input is refused up front only in a minimized window (untested there).
- chrome_scroll scrolls hidden pages by script instead of the wheel.
- Focus emulation on attach, so blur-sensitive menus stay open.
- Background mode is off by default. Calls still default to background;
  background:false or chrome_tab activate brings a tab forward.
- Agent guidance, tool descriptions and docs say so.

1 files changed, 0 insertions, 61 deletions

diff --git a/test-suite/unit/shared-window.test.mjs b/test-suite/unit/shared-window.test.mjs
deleted file mode 100644
index 66041f4..0000000
--- a/test-suite/unit/shared-window.test.mjs
+++ /dev/null
@@ -1,61 +0,0 @@
-// Each session has its own window: a window shows only one tab, so sessions sharing one hid each
-// other's tabs (no real input, blank screenshots). A session's extra tabs go into its own window.
-import assert from "node:assert/strict";
-import fs from "node:fs";
-import vm from "node:vm";
-import { test } from "node:test";
-
-const workerSource = fs.readFileSync(new URL("../../extensions/chrome-profile-bridge/browser-extension/service_worker.js", import.meta.url), "utf8");
-
-function worker({ groups = [], windows = { 5: { id: 5, type: "normal" } } } = {}) {
-  const calls = [];
-  const listener = { addListener() {}, removeListener() {} };
-  let nextTab = 100;
-  const w = {
-    console, setTimeout, clearTimeout, setInterval: () => 0, navigator: { userAgent: "unit-test" }, fetch: async () => { throw new Error("offline"); },
-    chrome: {
-      runtime: { id: "test", getManifest: () => ({ version: "0.0.0" }), onInstalled: listener, onStartup: listener },
-      alarms: { create() {}, onAlarm: listener }, action: { onClicked: listener }, webNavigation: { onCommitted: listener },
-      debugger: { onDetach: listener, onEvent: listener, getTargets: (cb) => cb([]) },
-      storage: { session: { get: async () => ({}), set: async (v) => { calls.push({ method: 'storage.set', json: JSON.stringify(v) }); } } },
-      tabGroups: { query: async () => groups },
-      windows: {
-        get: async (id) => windows[id] ?? Promise.reject(new Error("No window")),
-        create: async (props) => { calls.push({ method: "windows.create", props }); return { id: 9, tabs: [{ id: 900, windowId: 9 }] }; },
-      },
-      tabs: {
-        create: async (props) => { calls.push({ method: "tabs.create", props }); return { id: nextTab++, windowId: props.windowId }; },
-        query: async () => [], get: async () => null, onUpdated: listener,
-      },
-    },
-  };
-  w.self = w;
-  vm.runInNewContext(workerSource, w);
-  return { w, calls };
-}
-
-const piGroup = (windowId, name = "Pi Session: claude-code 1 other") => ({ id: 1, windowId, title: name });
-const ops = (calls) => calls.filter((c) => c.method !== "storage.set").map((c) => c.method);
-
-test("a new session gets its own window even when another session's window exists", async () => {
-  const { w, calls } = worker({ groups: [piGroup(5)] });
-  await w.createAutomationTarget("claude-code 2 mine", "Pi Session: claude-code 2 mine");
-  assert.deepEqual(ops(calls), ["windows.create"]);
-});
-
-test("a session that already has a group adds its tab to that group's window", async () => {
-  const { w, calls } = worker({ groups: [piGroup(5, "Pi Session: claude-code 2 mine")] });
-  await w.createAutomationTarget("claude-code 2 mine", "Pi Session: claude-code 2 mine");
-  assert.deepEqual(ops(calls), ["tabs.create"]);
-  assert.equal(calls.find((c) => c.method === "tabs.create").props.windowId, 5);
-});
-
-test("chrome_tab new for a session with no group goes to the session's own window, not the focused one", async () => {
-  const { w, calls } = worker({ groups: [piGroup(5)] });
-  w.groupTab = async (tab) => tab;
-  w.bringToFront = async () => {};
-  await w.dispatch("tab.new", { url: "https://x.test/", groupTitle: "Pi Session: claude-code 2 mine", sessionKey: "claude-code 2 mine" });
-  assert.deepEqual(ops(calls), ["windows.create"]);
-  assert.equal(calls[0].props.url, "https://x.test/");
-  assert.equal(calls[0].props.focused, false);
-});