ids theme: reliably render "Authors (Year):" as bold first line in bibliography

The old CSS hack inserted a line break before the FIRST ELEMENT CHILD of
each .csl-entry, plus a ::first-line tint. Which part of an entry
citeproc wraps in spans anchors depends on the entry type, so the break
landed arbitrarily -- e.g. mid-title in the DeLiKo entry or before the
final URL. Replace it with an explicit wrap: the theme template walks
the leading text nodes of each entry to the first "):" and marks them
as .csl-authors-year (display: block; bold; mid blue-gray), which is
both the bold first line and the line break. Entries without a year
marker are left untouched; spacing between entries is restored with a
0.5em margin (pandoc's div.csl-entry pins it to 0em otherwise). The
demo bibliography gains the DeLiKo citation as a regression case.

Change-Id: I196368e631a8870d63fe2022fb5cda3a0ad30072
diff --git a/examples/references.bib b/examples/references.bib
index 7a73b87..4d09137 100644
--- a/examples/references.bib
+++ b/examples/references.bib
@@ -20,3 +20,15 @@
         pages = {7015--7021},
 }
 
+@inproceedings{kupietz-deliko2026,
+  title = {National Library as Corpus – {DeLiKo-2025@DNB}: a Very Large Corpus of {German}-language Contemporary Literature},
+  author = {Kupietz, Marc and Diewald, Nils and Genêt, Philippe and Witt, Andreas},
+  booktitle = {Proceedings of the Fifteenth Language Resources and Evaluation Conference (LREC 2026)},
+  month = {May},
+  year = {2026},
+  pages = {6528--6535},
+  address = {Palma, Mallorca, Spain},
+  publisher = {European Language Resources Association (ELRA)},
+  editor = {Piperidis, Stelios and Bel, Núria and van den Heuvel, Henk and Ide, Nancy and Krek, Simon and Toral, Antonio},
+  doi = {10.63317/59wsms6588ys},
+}