NotificationProjector now also consumes interaction.normalized and, for kind
EMAIL (external email + app-to-app mail, which land via ingest — not
message.sent), always notifies the non-sender recipient(s), reusing the same
presence + mute gates. Refactors the fan-out into a shared notify() with an
alwaysNotify flag (DM or mail); message.sent keeps its DM/mention/reply policy.
Adds specs: mail notifies in a group thread where a plain message would not, and
a non-EMAIL normalized interaction does not notify.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
maaz519
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