p3: tavily parse errors degrade; retry DNS on search

A 200 with a bad Tavily body is tavily: error, not an empty success
that would cache for the hour. Upstream clients stay in the source
list if DNS is down at boot and retry the pin on Search; /healthz
lists them as unresolved until a pin lands.

internal/search/tavily.go

@@ -17,6 +17,7 @@ type Tavily struct {
 }
 
 func (s *Tavily) Name() string { return NameTavily }
+func (s *Tavily) Ready() bool  { return s != nil && s.Client.Ready() }
 
 type tavilyReq struct {
 	Query             string `json:"query"`
@@ -31,7 +32,9 @@ func (s *Tavily) Search(ctx context.Context, query string, k int) SourceOut {
 	if s == nil || s.Client == nil {
 		return SourceOut{Warn: NameTavily + ": error"}
 	}
-	_ = s.Client.RefreshIfStale(ctx)
+	if w := pinErr(ctx, s.Client, NameTavily); w != "" {
+		return SourceOut{Warn: w}
+	}
 	if k <= 0 {
 		k = DefaultK
 	}
@@ -66,11 +69,14 @@ func (s *Tavily) Search(ctx context.Context, query string, k int) SourceOut {
 	if err != nil {
 		return SourceOut{Warn: warnErr(NameTavily, err)}
 	}
-	hits, credits := mapTavily(raw)
+	hits, credits, err := mapTavily(raw)
+	if err != nil {
+		return SourceOut{Warn: NameTavily + ": error"}
+	}
 	return SourceOut{Hits: hits, Credits: credits}
 }
 
-func mapTavily(raw []byte) ([]Hit, int) {
+func mapTavily(raw []byte) ([]Hit, int, error) {
 	var env struct {
 		Answer  string `json:"answer"`
 		Results []struct {
@@ -84,7 +90,7 @@ func mapTavily(raw []byte) ([]Hit, int) {
 		} `json:"usage"`
 	}
 	if err := json.Unmarshal(raw, &env); err != nil {
-		return nil, 0
+		return nil, 0, err
 	}
 	_ = env.Answer // dropped; never returned
 	hits := make([]Hit, 0, len(env.Results))
@@ -98,5 +104,5 @@ func mapTavily(raw []byte) ([]Hit, int) {
 	if credits <= 0 {
 		credits = 1
 	}
-	return hits, credits
+	return hits, credits, nil
 }