The server and the core each derived display_title and disagreed twice: the
server cut it at 200 characters and the core didn't, and the server split lines
with splitlines(), which also breaks on a lone \r or a U+2028, where the core and
every other reading of the grammar split on \n alone.
- grammar.json gains a display_titles section: blank lines, markers, an empty
item, \r\n, a lone \r, U+2028, and a 201-character line of 'é' (the cut is
characters, not bytes).
- derive::display_title and DISPLAY_TITLE_CAP are the core's half, moved next to
strip_marker. The server splits on "\n". Both suites run the cases.
Behaviour: a device now names a note with a first line over 200 characters the
way the web always has, and the server names a note containing a lone \r or a
U+2028 the way devices always have.
Fixes#5398. DRY pass #2, batch 3 (#5372).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>