fix: migrate chat.md from instructions to inline $facets, update baselines
muse/chat.md was created by the identity refactor after the feature
branch diverged, so the template unification never migrated it. Remove
the obsolete instructions frontmatter and add $facets inline. Regenerate
all API baselines to match.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>