refactor: cut the engine's backtest-metrics edge via RunReport<M>

C28 phase 2 (Stratification); realizes item 1 of the deferred #147. The
engine's production surface no longer names a backtest-metric type:

- RunReport becomes generic over its metric payload M; sweep/mc/walkforward/
  blueprint thread the parameter (SweepPoint<M>, SweepFamily<M>, WindowRun<M>,
  WalkForwardResult<M>). RunManifest stays concrete and engine-owned (its
  selection: Option<FamilySelection> embeds the foundation-grade analysis type).
- summarize and the MC assembly (McDraw/McFamily/McAggregate/RBootstrap/
  r_bootstrap/monte_carlo) move to aura-backtest - McAggregate::from_draws reads
  RunMetrics fields by name, so generifying it is the phase-6 metric-vocabulary
  abstraction (#147 item 2), still deferred; wholesale relocation is the honest
  cut. The concrete instantiation lives in aura-backtest as
  `type RunReport = aura_engine::RunReport<RunMetrics>` + sibling aliases.
- the statistics kernel (MetricStats/quantile/resample_block/SplitMix64) moves
  to the aura-analysis foundation; the engine re-imports it (inner->foundation,
  legal) and re-exports it so existing consumers stay source-compatible.

Dependency inversion in one commit: aura-engine drops aura-backtest from
[dependencies] (back to dev-deps for its SimBroker/RunMetrics test fixtures);
aura-backtest gains aura-engine. Cycle-free for lib targets - the cycle closes
only through the engine's dev-dep edge, the pattern aura-vocabulary already
uses. aura-backtest reaches the kernel transitively through the engine
re-export, so no aura-backtest -> aura-analysis edge exists (the C28 ladder
permits backtest -> {core, engine} only). run_indexed / SplitMix64::next_f64
widened pub(crate) -> pub for cross-crate use.

Consumers (registry/campaign/cli/composites/ingest/bench) rewired by import
path only, no call-site logic changed. The c28_layering structural test extends
to the full ladder: aura-analysis (no aura-* deps), aura-engine ⊆ {core,
analysis}, aura-backtest ⊆ {core, engine}.

Behaviour-preserving: 1448/0 tests, clippy -D warnings clean, serde shapes
byte-identical (C18 - RunReport<M> keeps field order manifest,metrics; the
CLI pre-serialized-splice contract unchanged), moved code traceable via git
rename detection. Cycle-introduced broken intra-doc links fixed.

closes #292

crates/aura-ingest/examples/ger40_breakout_compare.rs

@@ -24,7 +24,7 @@
 use std::sync::Arc;
 
 use aura_core::{Cell, Scalar, Timestamp};
-use aura_engine::{summarize, RunMetrics};
+use aura_backtest::{summarize, RunMetrics};
 use chrono_tz::Europe::Berlin;
 
 use aura_ingest::{default_data_server, open_ohlc, DataServer, DEFAULT_DATA_PATH};

crates/aura-ingest/examples/ger40_breakout_sweep.rs

@@ -16,7 +16,8 @@
 use std::sync::Arc;
 
 use aura_core::{Cell, Scalar, Timestamp};
-use aura_engine::{sweep, summarize, GridSpace, RunManifest, RunReport};
+use aura_backtest::{summarize, RunReport};
+use aura_engine::{sweep, GridSpace, RunManifest};
 use chrono_tz::Europe::Berlin;
 use aura_ingest::{default_data_server, open_ohlc, DataServer, DEFAULT_DATA_PATH};
 

crates/aura-ingest/examples/ger40_breakout_walkforward.rs

@@ -18,9 +18,10 @@
 use std::sync::Arc;
 
 use aura_core::{Cell, Scalar, Timestamp};
+use aura_backtest::{summarize, RunReport, WindowRun};
 use aura_engine::{
-    sweep, summarize, walk_forward, GridSpace, RollMode, RunManifest, RunReport, WindowBounds,
-    WindowRoller, WindowRun,
+    sweep, walk_forward, GridSpace, RollMode, RunManifest, WindowBounds,
+    WindowRoller,
 };
 use chrono::TimeZone;
 use chrono_tz::Europe::Berlin;

crates/aura-ingest/examples/shared/breakout_real.rs

@@ -40,10 +40,10 @@ use std::sync::mpsc;
 
 use aura_core::{NodeSchema, Scalar, ScalarKind, Timestamp};
 use aura_engine::{
-    join_on_ts, summarize, Composite, Edge, FlatGraph, GraphBuilder, Harness, RunManifest,
-    RunReport, SourceSpec, Target,
+    join_on_ts, Composite, Edge, FlatGraph, GraphBuilder, Harness, RunManifest,
+    SourceSpec, Target,
 };
-use aura_backtest::SimBroker;
+use aura_backtest::{summarize, RunReport, SimBroker};
 use aura_market::{Resample, Session};
 use aura_std::{And, Delay, EqConst, Gt, Latch, Recorder};
 use chrono::TimeZone;

crates/aura-ingest/tests/ger40_breakout_real.rs

@@ -31,7 +31,7 @@ fn run_real(
     server: &Arc<DataServer>,
     from: Timestamp,
     to: Timestamp,
-) -> (aura_engine::RunReport, Vec<(f64, f64)>) {
+) -> (aura_backtest::RunReport, Vec<(f64, f64)>) {
     let sources =
         open_ohlc(server, SYMBOL, from, to).expect("GER40 has data in the Sept-2024 window");
     let (mut h, taps) = build_harness();

crates/aura-ingest/tests/ger40_breakout_world.rs

@@ -21,9 +21,10 @@
 use std::sync::Arc;
 
 use aura_core::{Cell, Scalar, Timestamp};
+use aura_backtest::{summarize, RunReport, WindowRun};
 use aura_engine::{
-    sweep, summarize, walk_forward, GridSpace, RollMode, RunManifest, RunReport, WindowBounds,
-    WindowRoller, WindowRun,
+    sweep, walk_forward, GridSpace, RollMode, RunManifest, WindowBounds,
+    WindowRoller,
 };
 use chrono::TimeZone;
 use chrono_tz::Europe::Berlin;

crates/aura-ingest/tests/real_bars.rs

@@ -9,11 +9,11 @@ use std::sync::Arc;
 
 use aura_core::{Firing, NodeSchema, PortSpec, Scalar, ScalarKind, Timestamp};
 use aura_engine::{
-    f64_field, summarize, Edge, FlatGraph, Harness, RunManifest, RunReport, SourceSpec, Target,
+    f64_field, Edge, FlatGraph, Harness, RunManifest, SourceSpec, Target,
     VecSource,
 };
 use aura_ingest::load_m1_window;
-use aura_backtest::SimBroker;
+use aura_backtest::{summarize, RunReport, SimBroker};
 use aura_std::{Recorder, Sma, Sub};
 use aura_strategy::Bias;
 use data_server::{DataServer, DEFAULT_DATA_PATH};

crates/aura-ingest/tests/streaming_seam.rs

@@ -9,11 +9,11 @@ use std::sync::Arc;
 
 use aura_core::{Firing, NodeSchema, PortSpec, Scalar, ScalarKind, Timestamp};
 use aura_engine::{
-    f64_field, summarize, Edge, FlatGraph, Harness, RunManifest, RunReport, Source, SourceSpec,
+    f64_field, Edge, FlatGraph, Harness, RunManifest, Source, SourceSpec,
     Target,
 };
 use aura_ingest::{M1Field, M1FieldSource};
-use aura_backtest::SimBroker;
+use aura_backtest::{summarize, RunReport, SimBroker};
 use aura_std::{Recorder, Sma, Sub};
 use aura_strategy::Bias;
 use data_server::loader::CHUNK_SIZE;