The runner was calling splitStatements(string) directly on migration['up']
without checking whether it was a Closure, causing a fatal type error on
all idempotent closure-based migrations (Phase_94_001, _002, Phase_96_001).
Now checks is_callable() first and invokes the closure, falling back to
string SQL splitting for plain-string migrations.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>