feat(search): P3.1 filters and multi-query merge

Native include/exclude domains, time_range, topic, exact_match, min_score,
and up to 4 queries fused with RRF. Honesty notes stay off the Warn/fail
path. Tavily keeps include_answer false and sets auto_parameters false.
Cache key is canonical JSON. CLI flags and skill recipe included.

internal/search/tavily.go

@@ -19,16 +19,7 @@ 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"`
-	MaxResults        int    `json:"max_results"`
-	IncludeAnswer     bool   `json:"include_answer"`
-	IncludeRawContent bool   `json:"include_raw_content"`
-	IncludeImages     bool   `json:"include_images"`
-	SearchDepth       string `json:"search_depth"`
-}
-
-func (s *Tavily) Search(ctx context.Context, query string, k int) SourceOut {
+func (s *Tavily) Search(ctx context.Context, query string, k int, f Filter) SourceOut {
 	if s == nil || s.Client == nil {
 		return SourceOut{Warn: NameTavily + ": error"}
 	}
@@ -41,14 +32,7 @@ func (s *Tavily) Search(ctx context.Context, query string, k int) SourceOut {
 	if k > 20 {
 		k = 20
 	}
-	payload, _ := json.Marshal(tavilyReq{
-		Query:             query,
-		MaxResults:        k,
-		IncludeAnswer:     false,
-		IncludeRawContent: false,
-		IncludeImages:     false,
-		SearchDepth:       "basic",
-	})
+	payload, _ := json.Marshal(tavilyBody(query, k, f))
 	req, err := http.NewRequestWithContext(ctx, http.MethodPost, s.Client.URL.String(), bytes.NewReader(payload))
 	if err != nil {
 		return SourceOut{Warn: warnErr(NameTavily, err)}
@@ -76,14 +60,58 @@ func (s *Tavily) Search(ctx context.Context, query string, k int) SourceOut {
 	return SourceOut{Hits: hits, Credits: credits}
 }
 
+func tavilyBody(query string, k int, f Filter) map[string]any {
+	body := map[string]any{
+		"query":               query,
+		"max_results":         k,
+		"include_answer":      false,
+		"include_raw_content": false,
+		"include_images":      false,
+		"search_depth":        "basic",
+		"auto_parameters":     false,
+	}
+	if len(f.IncludeDomains) > 0 {
+		body["include_domains"] = f.IncludeDomains
+		mode := f.IncludeDomainsMode
+		if mode == "" {
+			mode = "restrict"
+		}
+		body["include_domains_mode"] = mode
+	}
+	if len(f.ExcludeDomains) > 0 {
+		body["exclude_domains"] = f.ExcludeDomains
+	}
+	if f.TimeRange != "" {
+		body["time_range"] = f.TimeRange
+	} else {
+		if f.StartDate != "" {
+			body["start_date"] = f.StartDate
+		}
+		if f.EndDate != "" {
+			body["end_date"] = f.EndDate
+		}
+	}
+	if f.Topic != "" && f.Topic != "general" {
+		body["topic"] = f.Topic
+	}
+	if f.ExactMatch {
+		body["exact_match"] = true
+	}
+	if f.Topic == "news" || f.TimeRange != "" || f.StartDate != "" || f.EndDate != "" {
+		body["include_published_date"] = true
+	}
+	return body
+}
+
 func mapTavily(raw []byte) ([]Hit, int, error) {
 	var env struct {
 		Answer  string `json:"answer"`
 		Results []struct {
-			URL     string  `json:"url"`
-			Title   string  `json:"title"`
-			Content string  `json:"content"`
-			Score   float64 `json:"score"`
+			URL           string  `json:"url"`
+			Title         string  `json:"title"`
+			Content       string  `json:"content"`
+			Score         float64 `json:"score"`
+			PublishedDate string  `json:"published_date"`
 		} `json:"results"`
 		Usage struct {
 			Credits int `json:"credits"`
@@ -98,7 +126,10 @@ func mapTavily(raw []byte) ([]Hit, int, error) {
 		if r.URL == "" {
 			continue
 		}
-		hits = append(hits, Hit{URL: r.URL, Title: r.Title, Snippet: r.Content, Score: r.Score, Source: NameTavily})
+		hits = append(hits, Hit{
+			URL: r.URL, Title: r.Title, Snippet: r.Content,
+			Score: r.Score, Source: NameTavily, PublishedDate: r.PublishedDate,
+		})
 	}
 	credits := env.Usage.Credits
 	if credits <= 0 {