Reversal of the language decision from 6d94fa5. Texts that get
committed to the repo permanently should follow the same English-
only rule as everything else; the Notify push stays 1:1 with the
WhatsNew entry, so both are English now.
The "only file intentionally not in English" carve-out in CLAUDE.md
is removed.
Done-state notifications now produce two synchronised outputs sharing
one text: an entry appended to docs/WhatsNew.md and the same string
sent via notify.sh. The text is written in German for the user-as-
reader who did not watch the session — no technical internals, no
iteration codes, lead with the change-in-the-project.
WhatsNew.md is the only file in the repo intentionally not in English;
the exception is documented in CLAUDE.md (Roles of docs/...) so a
future reader does not "correct" it back. Bounce-back notifications
stay Notify-only.