feat: show scalar index type in ScalarIndexQuery plan output (#6677)

The ScalarIndexQuery (and MaterializeIndex) plan nodes now display the
underlying scalar index type (BTree, Bitmap, NGram, LabelList, etc.)
alongside the index name, e.g. `[category = 1]@category_idx(Bitmap)`.
This makes it easier to tell which kind of index is being used when
inspecting analyze/explain output without cross-referencing the
manifest.

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

Author: wkalt

rust/lance-index/src/scalar/bitmap.rs

@@ -1495,7 +1495,11 @@ impl ScalarIndexPlugin for BitmapIndexPlugin {
         index_name: String,
         _index_details: &prost_types::Any,
     ) -> Option<Box<dyn ScalarQueryParser>> {
-        Some(Box::new(SargableQueryParser::new(index_name, false)))
+        Some(Box::new(SargableQueryParser::new(
+            index_name,
+            self.name().to_string(),
+            false,
+        )))
     }
 
     async fn train_index(

rust/lance-index/src/scalar/bloomfilter.rs

@@ -1088,7 +1088,11 @@ impl ScalarIndexPlugin for BloomFilterIndexPlugin {
         index_name: String,
         _index_details: &prost_types::Any,
     ) -> Option<Box<dyn ScalarQueryParser>> {
-        Some(Box::new(BloomFilterQueryParser::new(index_name, true)))
+        Some(Box::new(BloomFilterQueryParser::new(
+            index_name,
+            self.name().to_string(),
+            true,
+        )))
     }
 
     async fn load_index(

rust/lance-index/src/scalar/btree.rs

@@ -2706,7 +2706,11 @@ impl ScalarIndexPlugin for BTreeIndexPlugin {
         index_name: String,
         _index_details: &prost_types::Any,
     ) -> Option<Box<dyn ScalarQueryParser>> {
-        Some(Box::new(SargableQueryParser::new(index_name, false)))
+        Some(Box::new(SargableQueryParser::new(
+            index_name,
+            self.name().to_string(),
+            false,
+        )))
     }
 
     async fn train_index(