fix(example): remove dead NeuralTagger reference from aspect_tagging_demo

NeuralTagger was imported and instantiated at line 7 + 104 but has never
existed in src/rust/aspect.rs (verified: zero `pub struct NeuralTagger`
matches anywhere in the workspace). The import broke
cargo check --example aspect_tagging_demo with E0432.

Removed the import + the .add_tagger(Box::new(NeuralTagger::new()), 0.5)
call. CompositeTagger now ships with the single RuleBasedTagger which
is what actually drives the demo. Left an inline comment for the future
neural tagger integration (likely via Julia /predict or src/rust/neural.rs).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

examples/aspect_tagging_demo.rs

@@ -4,7 +4,7 @@
 //! Example demonstrating aspect tagging system usage
 
 use echidna::aspect::{
-    AggregationStrategy, Aspect, AspectTagger, CompositeTagger, NeuralTagger, RuleBasedTagger,
+    AggregationStrategy, Aspect, AspectTagger, CompositeTagger, RuleBasedTagger,
 };
 use echidna::core::Term;
 
@@ -99,9 +99,12 @@ fn main() {
 
     // Example 6: Composite tagger with multiple strategies
     println!("6. Composite Tagger:");
+    // NOTE: a NeuralTagger was previously composed in here. It was a stub
+    // never landed in src/rust/aspect.rs, so the import + add_tagger call
+    // were dead. Removed 2026-04-25. Re-add when a real neural tagger
+    // ships (likely via the Julia /predict endpoint or src/rust/neural.rs).
     let composite = CompositeTagger::new(AggregationStrategy::WeightedVoting)
-        .add_tagger(Box::new(RuleBasedTagger::new()), 1.0)
-        .add_tagger(Box::new(NeuralTagger::new()), 0.5); // Neural tagger stub
+        .add_tagger(Box::new(RuleBasedTagger::new()), 1.0);
 
     let theorem_name = "functor_category_theory";
     let statement = Term::Const("functor".to_string());