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>

bulk-check.css

@@ -0,0 +1,102 @@
+body {
+  font-family: -apple-system, Segoe UI, sans-serif;
+  font-size: 13px;
+  margin: 0;
+  padding: 12px;
+  background: #1a1a1a;
+  color: #ddd;
+}
+
+#header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  margin-bottom: 8px;
+}
+#header strong { font-size: 15px; }
+
+#mode-pill {
+  font-size: 11px;
+  font-weight: 700;
+  letter-spacing: 0.4px;
+  background: #1a2a3a;
+  color: #6ec1ff;
+  padding: 2px 8px;
+  border-radius: 3px;
+  border: 1px solid #2a4a6a;
+}
+#mode-pill[data-mode="CACHE"] {
+  background: #1a3a1a;
+  color: #afa;
+  border-color: #2a5a2a;
+}
+
+.help {
+  font-size: 12px;
+  color: #aaa;
+  line-height: 1.4;
+  margin-bottom: 8px;
+}
+.help code {
+  background: #0d0d0d;
+  padding: 1px 4px;
+  border-radius: 2px;
+  font-family: Consolas, monospace;
+  color: #ddd;
+}
+.dim { color: #777; }
+
+textarea#bulk-id-input {
+  width: 100%;
+  height: 140px;
+  resize: vertical;
+  background: #0d0d0d;
+  color: #ddd;
+  border: 1px solid #444;
+  border-radius: 3px;
+  padding: 6px 8px;
+  font-size: 12px;
+  font-family: Consolas, monospace;
+  box-sizing: border-box;
+}
+textarea#bulk-id-input:focus { outline: none; border-color: #6ec1ff; }
+
+.button-row {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  margin: 8px 0;
+}
+
+button {
+  background: #333;
+  color: #ddd;
+  border: 1px solid #555;
+  border-radius: 3px;
+  padding: 4px 10px;
+  cursor: pointer;
+  font-size: 12px;
+}
+button:hover { background: #444; }
+button:disabled { opacity: 0.5; cursor: default; }
+button.running { background: #3a1a1a; border-color: #722; color: #faa; }
+
+#count-pill {
+  margin-left: auto;
+  font-size: 11px;
+}
+
+.mono-output {
+  background: #0d0d0d;
+  border: 1px solid #333;
+  border-radius: 3px;
+  padding: 8px 10px;
+  font-family: Consolas, monospace;
+  font-size: 12px;
+  line-height: 1.5;
+  max-height: 260px;
+  overflow-y: auto;
+  white-space: pre-wrap;
+  word-break: break-word;
+}
+.mono-output:empty { display: none; }