v1.9.99

Schema description fix (SH9 follow-up) and the v2.0 lock-ceremony recipe

• The root schema description still said --include-ecosystem "falls back to the
  bare array when no domain resolved," which SH9 (v1.9.95) removed. It now states
  the wrapper is always emitted, with error records under domains and an empty
  ecosystem_hyperedges on an all-failed batch. Both schema copies stay
  byte-identical; a readiness audit found this was the only stale reference left.
• Adds validation/v2.0-lock-ceremony.md, the exact mechanical steps to cut
  2.0.0 (G1 schema description bump, G2 fusion default-on with its test-update
  discipline, G4 changelog move and tag), so the lock is a well-understood pass
  rather than improvised at tag time.

Gate: full pytest, the schema tests.