si-LK: 5 more placeholder drops beyond #12097 (count, authorName, exportColorScheme/exportSelection, shortcut)

Following up on #12097 / #12109 — running the same placeholder-parity check against current si-LK.json, I found 5 more instances of the same bug class that aren't covered by #12109's new test suite (which explicitly documents si-LK as exempt from the missing-placeholder check).

These are additive to #12097's 3 si-LK findings, not a repeat of them — different keys entirely.

Dropped placeholders (value silently lost)

alerts.removeItemsFromsLibrary — missing {{count}}

• en: Delete {{count}} item(s) from library?
• si-LK: පුස්තකාලයෙන් අයිතම ඉවත් කරන්න

publishSuccessDialog.content — missing {{authorName}}

• en: Thank you {{authorName}}. Your library has been submitted for review...
• si-LK: ප්‍රකාශන සාර්ථකත්ව අන්තර්ගතය

toast.copyToClipboardAsPng — missing {{exportSelection}} and {{exportColorScheme}}

• en: Copied {{exportSelection}} to clipboard as PNG ({{exportColorScheme}})
• si-LK: PNG ලෙස ක්ලිප්බෝඩ් එකට පිටපත් කරන ලදි

toast.pasteAsSingleElement — missing {{shortcut}}

• en: Use {{shortcut}} to paste as a single element, or paste into an existing text editor
• si-LK: තනි අංගයක් ලෙස ඇලවීම

Notes

Found by diffing en.json against every other locale file's flattened keys and placeholder sets, filtered to exclude empty/untranslated strings (which fall back to English gracefully and aren't a bug).

Happy to open a PR inserting the placeholder tokens, but I don't speak Sinhala — would want a native speaker to confirm word order/grammar before merge. Also flagging: might be worth having #12109's parity test actually cover si-LK's missing-placeholder case too, since right now it's silently exempted and gaps like these can keep slipping through.