Fixture Series, Part 1

This is part 1 of a deliberately boring three-part fixture.

It exists to keep four things exercised on every build: series grouping, reading order, previous and next navigation, and — because these files live in a subfolder — the recursive content glob. A one-level glob used to drop nested posts silently, so this file failing to appear is itself the regression test.

Delete the whole fixture-series folder once real serialised writing replaces it.