v10.17 - Lineage-first phase selection and subphase enforcement

Summary

• enforce strict phase identity fall-through so AI checks current active phase first, then existing-family subphase fit, and only then a new major phase
• require visible why-not-current / why-not-subphase basis before new-major phase creation
• align touched runtime/design/changelog/master surfaces and keep the compact 18-rule runtime install/parity scope unchanged