Step 7a: Bulk ID Check moves to a detached popup window

New files:
  bulk-check.html, bulk-check.js, bulk-check.css

Popup gains a 📋 launcher button next to the ⚙ Options gear. Clicking
it sends `open-bulk-check` to background.js and closes the popup;
background.js owns window lifecycle:

  - chrome.storage.session.bulkCheckWindowId stashes the open window id
  - existing id → chrome.windows.update({ focused, drawAttention })
  - missing or stale id → chrome.windows.create({ type:'popup',
    width:640, height:540 }) and stash the new id
  - chrome.windows.onRemoved clears the stale id on close

Last-paste persisted to chrome.storage.local.bulkCheckLastPaste,
debounced 500ms on input, restored on window open. quickMode is read
from settings at run time, matching previous behavior. Ctrl/Cmd+Enter
inside the textarea triggers the check.

Options page no longer carries the Bulk ID Check fieldset: removed
from options.html (Library Review pdesc updated to note the
relocation) and the matching handlers from options.js
(1903 → 1852 lines). No manifest permission changes — own-page
chrome.windows.create needs no extra permission.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

background.js

@@ -692,6 +692,11 @@ chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
     })();
     return true;
   }
+  if (msg.type === "open-bulk-check") {
+    openBulkCheckWindow();
+    sendResponse({ ok: true });
+    return false;
+  }
   if (msg.type === "dupe-review") {
     (async () => {
       try {
@@ -1075,3 +1080,44 @@ chrome.runtime.onMessage.addListener((msg, sender, sendResponse) => {
 // On install / startup, build context menu
 chrome.runtime.onInstalled.addListener(() => ensureContextMenu());
 chrome.runtime.onStartup.addListener(() => ensureContextMenu());
+
+// ---------- Bulk Check standalone window ----------
+const BULK_CHECK_WIN_KEY = "bulkCheckWindowId";
+
+async function openBulkCheckWindow() {
+  const session = chrome.storage.session;
+  try {
+    const stored = session ? await session.get(BULK_CHECK_WIN_KEY) : {};
+    const existingId = stored?.[BULK_CHECK_WIN_KEY];
+    if (existingId) {
+      try {
+        await chrome.windows.update(existingId, { focused: true, drawAttention: true });
+        return;
+      } catch {
+        if (session) await session.remove(BULK_CHECK_WIN_KEY);
+      }
+    }
+    const win = await chrome.windows.create({
+      url: chrome.runtime.getURL("bulk-check.html"),
+      type: "popup",
+      width: 640,
+      height: 540,
+    });
+    if (session && win?.id != null) {
+      await session.set({ [BULK_CHECK_WIN_KEY]: win.id });
+    }
+  } catch (e) {
+    console.warn("openBulkCheckWindow failed:", e);
+  }
+}
+
+chrome.windows.onRemoved.addListener(async (windowId) => {
+  const session = chrome.storage.session;
+  if (!session) return;
+  try {
+    const stored = await session.get(BULK_CHECK_WIN_KEY);
+    if (stored?.[BULK_CHECK_WIN_KEY] === windowId) {
+      await session.remove(BULK_CHECK_WIN_KEY);
+    }
+  } catch { /* ignore */ }
+});