Step 6b: extract Library Issues from options.js

Continues the options.js split. New file:

  options-library-issues.js  453 lines

After this step:

  options-cache.js            161 lines
  options-dupe-review.js      616 lines
  options-library-issues.js   453 lines
  options.js                 1903 lines  (was 2356 after step 6)

Library Issues block was fully self-contained (lastLibraryIssues,
_libraryIssuesDirty, renderLibraryIssues, _closeLibraryIssues, and the
bottom IIFE wrapping _optScanTimer / _setOptScanningState /
_pollOptProgress for optimization-scan progress polling). No external
callers of its identifiers.

Reads _configuredScanRoots / _cacheSkippedByRemote and calls
rememberConfiguredScanRoots from options-cache.js by bare reference —
same cross-file binding pattern proven in step 6.

node --check passes on each file and on the concatenation of all four
files in load order. Concat = 3133 lines, matching pre-split total.

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

options.html

@@ -803,6 +803,7 @@
 
 <script src="options-cache.js"></script>
 <script src="options-dupe-review.js"></script>
+<script src="options-library-issues.js"></script>
 <script src="options.js"></script>
 </body>
 </html>