Per CTO directive — no wire compat, no alias, no shim. The R-LWE
threshold signature scheme is named Corona across all live Lux
code. Pre-2026-06 callers using "ringtail" must migrate to "corona"
on the procedure-routing surface.
- Drop schemeAliases map + canonicalScheme() from types.go.
- Delete TestCoronaRingtailWireAlias from thresholdd_test.go.
- protocols/parity test comment sweep.
Forward-only; no migration window, no fallback path.