The spec requires not_before on pending reminders only — terminal states
(done/cancelled) and bookmarks omit it. The validator incorrectly
required exactly one not_before on all kind:30300 events, blocking the
entire completion/cancellation lifecycle.
Also adds d-tag structure validation per spec: reject zero, empty, or
duplicate d tags.
Co-authored-by: Will Pfleger <will@pfleger.dev>
Signed-off-by: Will Pfleger <will@pfleger.dev>
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