chore: address PR review comments (comments, disjunction close, benchmarks)

- Restore the concise "clear out the score breakdown map" comment in
  DocumentMatch.Reset (keep the nil-guard).
- Drop the redundant fast-path comment in MergeFieldTermLocations.
- Split the combined err/rv check after the unadorned disjunction optimization
  into separate error and success returns, per review suggestion.
- Remove the standalone micro-benchmark files (merge_reset_bench_test.go,
  disj_unadorned_bench_test.go); the measurements live in the commit messages.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: capemox

index/scorch/disj_unadorned_bench_test.go

@@ -235,9 +235,7 @@ func (dm *DocumentMatch) Reset() *DocumentMatch {
 	}
 	// remember the score breakdown map
 	scoreBreakdown := dm.ScoreBreakdown
-	// clear out the score breakdown map; nil-guard because clear(nil) still
-	// dispatches through the map runtime (~1ns), and ScoreBreakdown is nil on
-	// the common path (no KNN, no score-breakdown retrieval)
+	// clear out the score breakdown map
 	if scoreBreakdown != nil {
 		clear(scoreBreakdown)
 	}

search/merge_reset_bench_test.go

@@ -68,17 +68,18 @@ func newDisjunctionSearcher(ctx context.Context, indexReader index.IndexReader,
 			optionsDisjunctionOptimizable(options) {
 			rv, err := optimizeCompositeSearcher(ctx, "disjunction:unadorned",
 				indexReader, qsearchers, options)
-			if err != nil || rv != nil {
-				if rv != nil {
-					// Finish() extracted all it needs (bitmaps are cloned/new).
-					// Close the original sub-searchers so their TFRs are returned
-					// to the snapshot per-field pool, avoiding re-allocation of
-					// Dictionary+FST Reader objects on the next query.
-					for _, s := range qsearchers {
-						_ = s.Close()
-					}
+			if err != nil {
+				return nil, err
+			}
+			if rv != nil {
+				// Finish() extracted all it needs (bitmaps are cloned/new).
+				// Close the original sub-searchers so their TFRs are returned
+				// to the snapshot per-field pool, avoiding re-allocation of
+				// Dictionary+FST Reader objects on the next query.
+				for _, s := range qsearchers {
+					_ = s.Close()
 				}
-				return rv, err
+				return rv, nil
 			}
 		}
 	}

search/search.go

@@ -55,7 +55,7 @@ func MergeFieldTermLocations(dest []FieldTermLocation, matches []*DocumentMatch)
 		}
 	}
 	if n == len(dest) {
-		return dest // fast path: no constituent has field term locations to merge
+		return dest
 	}
 	if cap(dest) < n {
 		dest = append(make([]FieldTermLocation, 0, n), dest...)