28e0331223
Architect audit clean (no drift): the derive is the faithful C10 book first-difference — Close uses the stored book volume (the actual book), never an exposure delta (the exact inversion of the abandoned 0064 exposure-integral); post-run reduction, no in-graph node (C14), positional type-erased Scalar reads (C7), each event's event_ts is its own cycle (C2), the >1-event-per-instant reversal case is why it is derived not per-eval (C8/C10); aura-engine -> aura-core only (instrument_id a caller scalar, no InstrumentSpec import). - Ledger C10: add a "Realization (cycle 0068, #115)" note — derive_position_events as the first difference of the executed book, the post-reframe replacement for the rolled-back 0064 derive; fixed-fractional / currency / equity-feedback sizing and the realistic brokers stay #116. - Remove the ephemeral spec + plan (cycle closed; rationale in the ledger + git history). Accepted low debt (architect [low]): the stop-then-same-cycle-reopen producer path emits the same closed&&open shape as a bias-flip reversal and the derive handles it correctly (it keys on closed/open/direction/size, not exit_reason; unit-covered via the reversal test), but is not separately asserted end-to-end. Cosmetic; the derive is producer-agnostic. refs #115