Accept whitespace as a separator after trigger words (e.g. "Applied in
master", "Fixed now"). However, keep strict punctuation-only matching
for :urgent and :important triggers, too prone to false positives in
ordinary prose (e.g. "Important settings:", "Important note:").

Also strip RFC 3676 email signatures ("-- ") from body before scanning
for commands.

Update docs/bark-manual.org to document accepted patterns and the
Important/Urgent exception.