Fixes a migration failure on databases provisioned before ec55a7a renamed the core schema from core to pontifex_mcp_core. Those databases never had a migration to perform the rename, so core_0005 (introduced in 0.5.0) would fail with schema "pontifex_mcp_core" does not exist on upgrade.
Fix
Adds migration core_0004b that conditionally renames the schema on existing installs and is a no-op on fresh ones.
Upgrading from 0.5.0
Run pontifex-mcp db upgrade — core_0004b and core_0005 will apply in sequence.
Upgrading from < 0.5.0
Follow the 0.5.0 upgrade notes, then run pontifex-mcp db upgrade.
Full Changelog: v0.5.0...v0.5.1