Review follow-up.
The two strings this branch adds carried no translator context: the
"Clear Filtered" tooltip in ClipboardHeader and the confirmation body for
a filtered clear in ClipboardHistoryContent. Both now say where they
appear, and the second one names what %1 is, per CONTRIBUTING.
"Clear All" on the same line is deliberately left alone. It is an
existing shared term with four other call sites, so a context there would
attach a clipboard-specific comment to a term the printer tab also uses.
clipboard.deleteEntries was handled but absent from the IPC method
listing that `dms debug-srv` prints, which left it undiscoverable right
next to clipboard.deleteEntry.
Catalogs untouched.