Hosting plan + docs aligned to one canonical fact sheet

docs/HOSTING.md — the stellate.app plan, argued from verified facts: a small DO droplet + nginx with ALL media same-origin (COOP/COEP require-corp for the SAB ring engine disqualifies DO Spaces — no CORP headers for the no-cors loads — and App Platform static — no custom headers at all)

• Docs alignment: README and CLAUDE.md finish the STELLATE rename, gain Open source + how.html + HOSTING pointers, and the submodule leaves the golden setup path (optional; public clones run without it).

▶ read how a song is made — the drawn pipeline itself https://stellate.app/how.html

7d02d65 https://github.com/aboard-io/stellate/commit/7d02d6555ee755c814463229a8c5718350362841