Take model tuning from config too, not from the saved state

The companion to the Kalman fix. RecursiveLeastSquares.from_dict and
AdaptiveConformal.from_dict restore lambda, delta, alpha, gamma and the
conformal window alongside their data, and load_dict replaces the
config-built heads with those, so every one of those knobs was immutable on
any station that already had state. Editing config.yaml and restarting looks
exactly like a change with no effect, which is the failure mode that cost real
time on the Kalman side of this before it was found.

Only the estimate is state now. Weights, covariances and conformal scores are
restored; tuning is re-applied from config on every load. The conformal deques
are rebuilt when the configured window changes, preserving their contents.

load_dict also skips heads for a target or horizon this build no longer has,
rather than resurrecting them from a stale file.

Found while implementing a damped-trend ensemble member, which was then
abandoned: see the following note.

ashvale/models/nowcast.py

@@ -151,6 +151,7 @@ class NowcastEnsemble:
                  cfg_model):
         self.targets = tuple(targets)
         self.horizons = tuple(int(h) for h in horizons_s)
+        self.cfg = cfg_model
         self.grid_s = int(cfg_model.grid_s)
         self.scaler = Standardiser(N_FEATURES)
         self.heads: Dict[Tuple[str, int], ForecastHead] = {
@@ -306,6 +307,27 @@ class NowcastEnsemble:
         self.scaler = Standardiser.from_dict(s["scaler"])
         for hs in s["heads"]:
             head = ForecastHead.from_dict(hs)
-            self.heads[(head.target, head.horizon_s)] = head
+            key = (head.target, head.horizon_s)
+            if key not in self.heads:
+                continue          # a target or horizon this build no longer has
+            self.heads[key] = head
         self.trained_rows = s.get("trained_rows", 0)
         self.refit_phase = int(s.get("refit_phase", 0))
+        self._apply_config_tuning()
+
+    def _apply_config_tuning(self) -> None:
+        """Tuning comes from config; only the estimate comes from the file.
+
+        Every from_dict below this point restores its knobs alongside its data:
+        lambda, delta and p_max in the RLS, alpha, gamma and the window in the
+        conformal calibrator. So each of those was immutable in the field. Edit
+        config.yaml, restart, and the state file quietly puts the old value
+        back, which looks exactly like a change that had no effect. The same
+        defect cost a Kalman retune here before it was found.
+        """
+        c = self.cfg
+        for head in self.heads.values():
+            head.model.lam = float(c.rls_forgetting)
+            head.model.delta = float(c.rls_delta)
+            head.conformal.retune(c.conformal_alpha, c.conformal_gamma,
+                                  c.conformal_window)