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/engine.go

@@ -2,7 +2,6 @@ package search
 
 import (
 	"context"
-	"encoding/json"
 	"log/slog"
 	"sort"
 	"sync"
@@ -90,104 +89,7 @@ func (e *Engine) timeout() time.Duration {
 }
 
 func (e *Engine) Run(ctx context.Context, query string, k int, doRerank bool, caller, class string) RunResult {
-	start := e.now()
-	k = ClampK(k, e.DefaultK)
-	if e.DefaultK <= 0 {
-		k = ClampK(k, DefaultK)
-	}
-	if class == "" {
-		class = dcache.ClassFleet
-	}
-
-	attempted := e.attemptedNames(class)
-	key := dcache.SearchKey(query, attempted, k, e.now(), class)
-	if b, ok := e.Cache.GetSearch(key); ok {
-		var hits []Hit
-		if json.Unmarshal(b, &hits) == nil {
-			e.mu.Lock()
-			e.CacheHit++
-			e.mu.Unlock()
-			return RunResult{Hits: clampHits(hits, k), Cached: true, Attempted: attempted, SearchMS: e.now().Sub(start).Milliseconds()}
-		}
-	}
-	e.mu.Lock()
-	e.CacheMiss++
-	e.mu.Unlock()
-
-	type one struct {
-		name string
-		out  SourceOut
-		skip bool
-	}
-	outs := make([]one, len(e.Sources))
-	var wg sync.WaitGroup
-	for i, src := range e.Sources {
-		name := src.Name()
-		if name == NameTavily && e.tavilyCapped(class) {
-			outs[i] = one{name: name, out: SourceOut{Warn: "tavily: daily cap"}, skip: true}
-			e.addCapped(NameTavily)
-			continue
-		}
-		wg.Add(1)
-		go func(i int, src Source, name string) {
-			defer wg.Done()
-			sctx, cancel := context.WithTimeout(ctx, e.timeout())
-			defer cancel()
-			outs[i] = one{name: name, out: src.Search(sctx, query, k)}
-		}(i, src, name)
-	}
-	wg.Wait()
-
-	var lists []namedHits
-	var hits []Hit
-	var warns []string
-	var okNames, failNames, att []string
-	degraded := false
-	for _, o := range outs {
-		if o.skip {
-			if o.out.Warn != "" {
-				warns = append(warns, o.out.Warn)
-			}
-			continue
-		}
-		att = append(att, o.name)
-		e.addQuery(caller, o.name)
-		if o.out.Warn != "" {
-			warns = append(warns, o.out.Warn)
-			failNames = append(failNames, o.name)
-			degraded = true
-			e.addErr(o.name, o.out.Warn)
-			continue
-		}
-		okNames = append(okNames, o.name)
-		lists = append(lists, namedHits{name: o.name, hits: o.out.Hits})
-		if o.out.Credits > 0 {
-			e.addCredits(caller, o.name, o.out.Credits)
-			if o.name == NameTavily && e.Cache != nil {
-				e.Cache.AddSearchCredits(tavilyCapSource(class), e.now().UTC().Format("2006-01-02"), o.out.Credits)
-			}
-		}
-	}
-	hits = mergeSearch(e, lists, doRerank)
-
-	var rerankMS int64
-	hits = clampHits(hits, k)
-
-	if !degraded && e.Cache != nil && len(att) > 0 {
-		payload, _ := json.Marshal(hits)
-		ck := dcache.SearchKey(query, att, k, e.now(), class)
-		e.Cache.PutSearch(ck, payload, e.ttl())
-	}
-
-	return RunResult{
-		Hits:          hits,
-		Warnings:      warns,
-		SourcesOK:     okNames,
-		SourcesFailed: failNames,
-		SearchMS:      e.now().Sub(start).Milliseconds(),
-		RerankMS:      rerankMS,
-		Attempted:     att,
-	}
+	return e.RunFilter(ctx, []string{query}, k, doRerank, caller, class, Filter{})
 }
 
 func (e *Engine) attemptedNames(class string) []string {