p3: map Brave LLM Context; RRF merge; per-source no_rerank

Live llm/context hits live in grounding.generic plus a URL-keyed
sources map, not a sources array. Fan-in uses reciprocal-rank fusion
instead of cosine. no_rerank keeps that source's own order as a prefix.

internal/search/sources_test.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"net/http"
 	"net/http/httptest"
+	"os"
 	"strings"
 	"testing"
 	"time"
@@ -96,6 +97,39 @@ func TestBraveMapsSources(t *testing.T) {
 	}
 }
 
+func TestBraveMapsGroundingGeneric(t *testing.T) {
+	raw, err := os.ReadFile("../../tests/testdata/brave_llm_context.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write(raw)
+	}))
+	defer ts.Close()
+	c, err := dial.New(ts.URL, dial.Options{Loopback: true, Timeout: time.Second})
+	if err != nil {
+		t.Fatal(err)
+	}
+	out := (&BraveLLM{Client: c, Key: "k"}).Search(context.Background(), "q", 5)
+	if len(out.Hits) != 3 {
+		t.Fatalf("hits %d %+v", len(out.Hits), out.Hits)
+	}
+	if out.Hits[0].URL != "https://docs.tavily.com/documentation/api-reference/endpoint/search" {
+		t.Fatalf("first %+v", out.Hits[0])
+	}
+	if !strings.Contains(out.Hits[0].Snippet, "max_results") {
+		t.Fatalf("snippet %q", out.Hits[0].Snippet)
+	}
+	var urls []string
+	for _, h := range out.Hits {
+		urls = append(urls, h.URL)
+	}
+	joined := strings.Join(urls, " ")
+	if !strings.Contains(joined, "orphan.example") {
+		t.Fatalf("sources map missed: %v", urls)
+	}
+}
+
 func TestTavilyBadJSONIsError(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		_, _ = w.Write([]byte(`not-json`))