Fix missing imports in SPO test modules (CausalLink, TruthValue, TypedHalo, SignificanceLevel)

Tests in gestalt.rs and causal_trajectory.rs used types that weren't
imported at module scope, causing compilation failures under --lib tests.

https://claude.ai/code/session_0152b2NJYnjCJjvMAmgsTx3p

Author: claude

src/spo/causal_trajectory.rs

@@ -34,16 +34,16 @@
 //! DN mutation guidance, and warm-start capability.
 
 use rustynum_bnn::causal_trajectory::{
-    CausalArrow, CausalChain, CausalDirection, CausalRelation, CausalSaliency,
+    CausalArrow, CausalChain, CausalDirection, CausalLink, CausalRelation, CausalSaliency,
     CausalTrajectory, DominantPlane,
     NarsCausalStatement, NarsTruth, ResonatorSnapshot, SigmaEdge,
 };
 use rustynum_bnn::{GrowthPath, InferenceMode, MutationOp};
-use rustynum_core::{CollapseGate, SigmaGate};
+use rustynum_core::{CollapseGate, SigmaGate, SignificanceLevel};
 
 use crate::nars::TruthValue;
 use super::gestalt::GestaltState;
-use super::spo_harvest::{Plane, SpoDistanceResult};
+use super::spo_harvest::{Plane, SpoDistanceResult, TypedHalo};
 use super::shift_detector::SpoShiftDetector;
 
 // =============================================================================

src/spo/gestalt.rs

@@ -761,7 +761,7 @@ impl AntialiasedSigma {
 // TACTIC #23 AMP: GestaltState → InferenceRuleKind bias
 // =============================================================================
 
-use crate::nars::InferenceRuleKind;
+use crate::nars::{InferenceRuleKind, TruthValue};
 use super::spo_harvest::AccumulatedHarvest;
 
 /// Per-rule bias vector derived from GestaltState.