refactor: split the aura-std roster into C28 layer crates

Phase 4 of the Stratification milestone. aura-std held four C28 ladder
layers in one roster; this cuts them into layer-aligned, aura-core-only
node crates so the import direction is enforced by the crate graph:

- aura-std        — engine nodes only (arithmetic/logic/rolling + sinks)
- aura-market     — session, resample
- aura-strategy   — bias, stops, sizer, cost-model machinery
- aura-backtest   — sim_broker, position_management
- aura-vocabulary — the relocated closed std_vocabulary roster

Node modules move verbatim (byte-identical renames); consumers are
rewired by import path only. A new structural test
(aura-vocabulary/tests/c28_layering.rs) asserts each node crate's
[dependencies] stay within its C28-permitted inner set, catching the
acyclic-but-outward violation the compiler misses.

Behaviour byte-identical: full workspace suite green (1448 tests), no
golden edited, clippy -D warnings clean. C28 Status block updated.

closes #288

crates/aura-cli/src/main.rs

@@ -30,16 +30,16 @@ use aura_registry::{
     FamilyMember, Generalization, NameKind, PlateauMode, Registry, RunTraces,
     DEFLATION_BLOCK_LEN, DEFLATION_N_RESAMPLES,
 };
+use aura_backtest::{SimBroker, PM_FIELD_NAMES, PM_RECORD_KINDS};
 use aura_std::{
-    cost_port, GatedRecorder, LinComb, Recorder, RollingMax, RollingMin,
-    SeriesReducer, SimBroker, Sub, GEOMETRY_WIDTH, PM_FIELD_NAMES,
-    PM_RECORD_KINDS,
+    GatedRecorder, LinComb, Recorder, RollingMax, RollingMin, SeriesReducer, Sub,
 };
+use aura_strategy::{cost_port, GEOMETRY_WIDTH};
 // `std_vocabulary` is now only reached through `project::Env::resolve` in production
 // code; the test module still builds reference blueprints against it directly, so
 // the import is test-only.
 #[cfg(test)]
-use aura_std::std_vocabulary;
+use aura_vocabulary::std_vocabulary;
 // `Delay` is now only used by the test-only `r_breakout_signal` carve (#159 cut 2's
 // fused-builder retirement dropped the production caller); the import is test-only.
 #[cfg(test)]
@@ -61,9 +61,11 @@ use aura_engine::ColumnarTrace;
 // `Bias`/`Ema`/`Sma` are only reached from the test module; the imports are
 // test-only, mirroring `Delay`/`Scale` above.
 #[cfg(test)]
-use aura_std::{Bias, Ema, Sma};
+use aura_strategy::Bias;
 #[cfg(test)]
-use aura_std::{ConstantCost, VolSlippageCost};
+use aura_std::{Ema, Sma};
+#[cfg(test)]
+use aura_strategy::{ConstantCost, VolSlippageCost};
 use std::sync::mpsc;
 use std::sync::LazyLock;
 use std::collections::{BTreeMap, BTreeSet, HashSet};