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/engines/braveapi.go

@@ -30,13 +30,9 @@ import (
 	"github.com/metamorphosis-dev/kafka/internal/contracts"
 )
 
-// BraveEngine implements the `braveapi` engine (Brave Web Search API).
-//
-// Config / gating:
-// - BRAVE_API_KEY: required to call Brave
-// - BRAVE_ACCESS_TOKEN (optional): if set, the request must include a token
-//   that matches the env var (via Authorization Bearer, X-Search-Token,
-//   X-Brave-Access-Token, or form field `token`).
+// BraveEngine implements the Brave Web Search API.
+// Required: BRAVE_API_KEY env var or config.
+// Optional: BRAVE_ACCESS_TOKEN to gate requests.
 type BraveEngine struct {
 	client          *http.Client
 	apiKey          string
@@ -51,8 +47,6 @@ func (e *BraveEngine) Search(ctx context.Context, req contracts.SearchRequest) (
 		return contracts.SearchResponse{}, errors.New("brave engine not initialized")
 	}
 
-	// Gate / config checks should not be treated as fatal errors; the reference
-	// implementation treats misconfigured engines as unresponsive.
 	if strings.TrimSpace(e.apiKey) == "" {
 		return contracts.SearchResponse{
 			Query:               req.Query,
@@ -109,8 +103,6 @@ func (e *BraveEngine) Search(ctx context.Context, req contracts.SearchRequest) (
 		}
 	}
 
-	// The reference implementation checks `if params["safesearch"]:` which treats any
-	// non-zero (moderate/strict) as strict.
 	if req.Safesearch > 0 {
 		args.Set("safesearch", "strict")
 	}