Walking Back Our v1.0 Announcement: Resetting to v0.9.0a1 as the First Build

Last week we announced v1.0 of stigmem, our federated agent memory project. That label was wrong. We're walking it back. And on review, the broader version history we'd been carrying (v0.2 through v2.0 across our spec files and versioned docs) was overstating the project's maturity in the same way.