feat(campaign,registry,engine): record widenings + preflight v2 fault set (0108 tasks 1-2)

Task 1: RBootstrap and Generalization gain serde derives;
lineage.rs gains StageBootstrap (per_survivor | pooled_oos) and
CampaignGeneralization; StageRealization.bootstrap and
CampaignRunRecord.generalizations land serde-default sparse (a
pre-0108 campaign_runs.jsonl line still parses — pinned), threaded
None/empty through every literal site. No behaviour change.

Task 2: ExecFault::UnsupportedStage is gone; the preflight now admits
the v2 shape sweep [gate]* [wf]? [mc]? [generalize]? via a monotone
rank walk (precise per-pair PipelineShape prose) and statically
refuses: single-instrument generalize (GeneralizeNeedsInstruments),
non-R generalize metrics via check_r_metric (GeneralizeNonRMetric —
no fourth roster site), zero mc params (ZeroBootstrapParam). CLI
prose swapped accordingly. The loop's E2E phase added a tier-boundary
pin: process validate accepts [sweep, mc, walk_forward] while campaign
run refuses it data-free.

KNOWN RED (documented in the plan, flips in task 5):
crates/aura-cli/tests/research_docs.rs::campaign_run_v1_boundary_refuses_mc_process
still pins the retired 'not executable in v1' prose. Interim gates:
registry 57/0, campaign 33/0, cli --bin 111/0, workspace build clean.

refs #200

crates/aura-engine/src/mc.rs

@@ -157,7 +157,7 @@ where
 /// (#139). `block_len == 1` is the i.i.d. trade-shuffle; `block_len > 1` resamples
 /// contiguous runs, preserving the serial correlation of sequential trades a pure
 /// shuffle would erase. Deterministic (C1) given `seed`.
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq, serde::Serialize, serde::Deserialize)]
 pub struct RBootstrap {
     pub e_r: MetricStats,   // mean + p5/p25/p50/p75/p95 of the resampled E[R]
     pub prob_le_zero: f64,  // fraction of resamples whose mean R <= 0