Mara 0.3.0

Breaking changes and migration

Schema format 3 is required. Review existing project vocabulary and authored
relations before editing the schema; existing projects do not acquire the new
engineering profile or its rules automatically. The Agent Plugin distribution
has been removed; configure MCP explicitly and install the matching skill
separately. Follow the 0.3 migration guide
for source edits, validation, and client interface changes.

Added

• Rebuild Mara around engineering traceability

Build

• Drop Intel macOS and speed verification