feat(campaign): expand the campaign matrix over risk regimes (#210 T3)

The regime becomes the fourth structural coordinate of the campaign matrix, a
kept-separate axis (a peer of window, not aggregated-over like instrument):

- aura-campaign: CellSpec gains `regime` + `regime_ordinal`; the executor
  resolves the regime list (absent/empty risk -> one default cell, ordinal 0),
  runs a cell per (strategy, instrument, window, regime), and keys the nominee
  map by the 3-tuple including the regime ordinal — so generalize aggregates
  across instruments WITHIN a regime, never across regimes. Family names gain a
  `-r{regime_ordinal}` discriminator so two regimes' families cannot collide.
- aura-registry: `CampaignGeneralization` gains `regime_ordinal` (with
  `#[serde(default)]`, so pre-feature stored records still parse — pinned by a
  new backward-compat test).

The existing single-regime execute tests shift their family ids by `-r0`; a new
test pins that two regimes yield distinct `-r0`/`-r1` families. `CellSpec.regime`
is write-only in this slice — its sole reader is the deferred member runner
(the next slice) — a held quality nit, seam-prep as the plan prescribes. Full
workspace suite green.

refs #210

crates/aura-registry/src/lib.rs

@@ -1852,6 +1852,7 @@ mod tests {
             generalizations: vec![CampaignGeneralization {
                 strategy_ordinal: 0,
                 window_ordinal: 0,
+                regime_ordinal: 0,
                 generalization: Some(Generalization {
                     selection_metric: "net_expectancy_r".to_string(),
                     n_instruments: 2,
@@ -1906,6 +1907,32 @@ mod tests {
         );
     }
 
+    /// Property (#210 T3, C14/C23 widening convention): a stored
+    /// `campaign_runs.jsonl` line whose `generalizations` entries predate the
+    /// risk-regime axis — carrying `strategy_ordinal`/`window_ordinal`/
+    /// `winners`/`missing` but no `regime_ordinal` key at all — still parses,
+    /// with `regime_ordinal` defaulting to 0 (`#[serde(default)]` on
+    /// `CampaignGeneralization::regime_ordinal`). Without that default, every
+    /// campaign-run store written before this iteration would fail to load
+    /// the instant it contained a recorded generalization.
+    #[test]
+    fn campaign_run_generalization_without_regime_ordinal_still_parses() {
+        let path = temp_family_dir("campaign_run_pre_regime_ordinal");
+        let store = path.with_file_name("campaign_runs.jsonl");
+        let line = r#"{"campaign":"cafe","process":"beef","run":0,"seed":7,"cells":[{"strategy":"3f9c","instrument":"EURUSD","window_ms":[0,1000],"stages":[{"block":"std::gate","survivor_ordinals":[0,2]}]}],"generalizations":[{"strategy_ordinal":0,"window_ordinal":0,"winners":[["EURUSD",[["fast.length",{"I64":3}]]]],"missing":["GER40"]}]}"#;
+        fs::write(&store, format!("{line}\n")).expect("write pre-regime-ordinal line");
+        let reg = Registry::open(&path);
+        let loaded = reg.load_campaign_runs().expect("pre-regime-ordinal generalization parses");
+        assert_eq!(loaded.len(), 1);
+        assert_eq!(loaded[0].generalizations.len(), 1);
+        assert_eq!(
+            loaded[0].generalizations[0].regime_ordinal, 0,
+            "a missing regime_ordinal key defaults to 0, not a parse failure"
+        );
+        assert_eq!(loaded[0].generalizations[0].strategy_ordinal, 0);
+        assert_eq!(loaded[0].generalizations[0].missing, vec!["GER40".to_string()]);
+    }
+
     /// The 0109 name composition (#201 d5 / the spec's seam note): a `Some`
     /// trace_name on the input record — the executor's claim sentinel,
     /// content ignored — is replaced on the STORED line with the derived

crates/aura-registry/src/lineage.rs

@@ -158,6 +158,11 @@ pub enum StageBootstrap {
 pub struct CampaignGeneralization {
     pub strategy_ordinal: usize,
     pub window_ordinal: usize,
+    /// The regime ordinal (0 for the default regime) — the third structural
+    /// coordinate, so a generalize grade is unambiguous per (strategy, window,
+    /// regime). `#[serde(default)]` keeps pre-feature stored records parsing.
+    #[serde(default)]
+    pub regime_ordinal: usize,
     /// None when fewer than 2 instrument cells produced a winner (gate
     /// truncation) — the shortfall is recorded, never computed around.
     #[serde(default, skip_serializing_if = "Option::is_none")]