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/qwant.go

@@ -30,11 +30,7 @@ import (
 	"github.com/PuerkitoBio/goquery"
 )
 
-// QwantEngine implements a `qwant` (web) adapter using
-// Qwant v3 endpoint: https://api.qwant.com/v3/search/web.
-//
-// Qwant's API is not fully documented; this implements parsing logic
-// for the `web` category.
+// QwantEngine implements the Qwant v3 API (web and web-lite modes).
 type QwantEngine struct {
 	client        *http.Client
 	category      string // "web" (JSON API) or "web-lite" (HTML fallback)
@@ -53,8 +49,6 @@ func (e *QwantEngine) Search(ctx context.Context, req contracts.SearchRequest) (
 		return contracts.SearchResponse{Query: req.Query}, nil
 	}
 
-	// For API parity we use web defaults: count=10, offset=(pageno-1)*count.
-	// The engine's config field exists so we can expand to news/images/videos later.
 	count := e.resultsPerPage
 	if count <= 0 {
 		count = 10
@@ -271,9 +265,7 @@ func (e *QwantEngine) searchWebLite(ctx context.Context, req contracts.SearchReq
 	results := make([]contracts.MainResult, 0)
 	seen := map[string]bool{}
 
-	// Pattern 1: legacy/known qwant-lite structure.
 	doc.Find("section article").Each(func(_ int, item *goquery.Selection) {
-		// ignore randomly interspersed advertising adds
 		if item.Find("span.tooltip").Length() > 0 {
 			return
 		}
@@ -307,19 +299,14 @@ func (e *QwantEngine) searchWebLite(ctx context.Context, req contracts.SearchReq
 		})
 	})
 
-	// Pattern 2: broader fallback for updated lite markup:
-	// any article/list item/div block containing an external anchor.
-	// We keep this conservative by requiring non-empty title + URL.
 	doc.Find("article, li, div").Each(func(_ int, item *goquery.Selection) {
 		if len(results) >= 20 {
 			return
 		}
-		// Skip ad-like blocks in fallback pass too.
 		if item.Find("span.tooltip").Length() > 0 {
 			return
 		}
 
-		// Skip obvious nav/footer blocks.
 		classAttr, _ := item.Attr("class")
 		classLower := strings.ToLower(classAttr)
 		if strings.Contains(classLower, "nav") || strings.Contains(classLower, "footer") {
@@ -368,13 +355,10 @@ func (e *QwantEngine) searchWebLite(ctx context.Context, req contracts.SearchReq
 		}
 		seen[href] = true
 
-		// Best-effort snippet extraction from nearby paragraph/span text.
 		content := strings.TrimSpace(item.Find("p").First().Text())
 		if content == "" {
 			content = strings.TrimSpace(item.Find("span").First().Text())
 		}
-		// If there is no snippet, still keep clearly external result links.
-		// Qwant-lite frequently omits rich snippets for some entries.
 
 		u := href
 		results = append(results, contracts.MainResult{