All nine derive-on-compose phases are now implemented. The status doc
captures what shipped per phase, what was deferred (LockedInDerived
override warning toast, SCADA008 base-Parent hint), and the live-DB /
UI smoke checks worth running before merge.
Phase 1 → 3 marked done; remaining work is phases 4-9. Sanity script now
targets the post-Phase-3 commit (03a8c4a) and notes the pre-existing
NU1608 build error in IntegrationTests / Host.Tests so future sessions
don't chase a phantom regression.
Companion to the design doc — captures current state, the four
decisions already made, what's done (phase 1, commit 5615f3d),
and a full play-by-play for phases 2 through 9 with exact files,
methods, and tests to touch. Written so a future session after
context compaction can pick up cleanly.
