Lands the first cycle of the "Cost-model graph (in R)" milestone: cost is
now a composable in-graph node, not a post-run scalar (C10).
- ConstantCost (aura-std): a flat round-trip cost per trade, emitted in R
as a 3-field record {cost_in_r, cum_cost_in_r, open_cost_in_r} isomorphic
to PositionManagement's R-triple. R-pure: cost_in_r = cost_per_trade /
|entry-stop|; notional cancels, no equity held.
- summarize_r folds the cost stream into net_expectancy_r, replacing its
scalar round_trip_cost (one home for cost, no double-count). Positional
co-temporal join; an empty stream is the gross-R baseline.
- net_r_equity tap (stage1_r_graph): LinComb(4) over [cum_realized_r,
unrealized_r, -cum_cost_in_r, -open_cost_in_r] -> Recorder, a sibling of
r_equity; --cost-per-trade on the run path wires the node + tap + fold.
- A no-cost run is byte-identical: no net_r_equity tap, net == gross, the
C18 golden unchanged.
Tests: exact-subsumption (the node-stream net == mean(r_i - cost_i) over
ALL trades incl. the window-end open one), the in-graph net_r_equity tap +
net < gross E2E, the no-cost golden held. Full suite green; clippy clean.
Implement-time decisions ratified (recorded on #148): the cost stream is
recorded 3-wide (the node's full output; summarize_r reads col 0/2, col 1
feeds the in-graph net curve) — resolving a 2-wide/3-wide inconsistency in
the plan's Step 3; Trade drops its `latched` field (cost now arrives in R),
so r_col ENTRY_PRICE/STOP_PRICE become #[allow(dead_code)] layout contract.
Scoped to the run path (non-reduce); sweep/walkforward/mc pass None — cost
on the reduce-mode sweep path and OOS-pooling cost are a deferred follow-up.
Known pre-existing concern (not this cycle): aura-std lib.rs module doc
still names "realistic broker profiles", retired by the C10 rework.
refs #148
Brummel
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