refactor: clean up verbose and redundant comments

Trim or remove comments that:
- State the obvious (function names already convey purpose)
- Repeat what the code clearly shows
- Are excessively long without adding value

Keep comments that explain *why*, not *what*.

internal/search/merge.go

@@ -25,11 +25,6 @@ import (
 )
 
 // MergeResponses merges multiple compatible JSON responses.
-//
-// MVP merge semantics:
-// - results are concatenated with a simple de-dup key (engine|title|url)
-// - suggestions/corrections are de-duplicated as sets
-// - answers/infoboxes/unresponsive_engines are concatenated (best-effort)
 func MergeResponses(responses []contracts.SearchResponse) contracts.SearchResponse {
 	var merged contracts.SearchResponse