Parse the occurrence field from sub_row and skip execution when today
is not the nth weekday specified (e.g. first_sunday). Check runs after
sub_row fetch but before dupe guard. Two new tests confirm skip and
pass paths using patched date.today in app.services.poster.
Replace hardcoded platform dispatch with get_client(campaign["type"]) so
any future campaign type (blog_post, email, etc.) routes automatically
through the strategy registry. Adds dupe-guard opt-out per strategy,
sub_row pre-fetch for extra metadata, and 5 new TDD tests (14 total).
