p3: search API, pinned sources, cache, CLI

POST /v1/search and /v2/search fan in SearXNG, Brave LLM Context, and
Tavily from config-fixed endpoints. Public sources refuse private A
records; SearXNG is a loopback-only client, not the fetch guard.

Cache keys include caller class. Restricted callers search like the
fleet; logs omit query, hosts, URLs, and upstream errors. Degraded
results are not stored. Tavily sends search_depth=basic and drops
answer. Missing keys surface in /healthz.

Default-on sources stay off until the bake-off. Query harvest is not
in this commit.

internal/search/dial/dial_test.go

@@ -0,0 +1,112 @@
+package dial_test
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"net/netip"
+	"net/url"
+	"strings"
+	"testing"
+
+	"git.wntrmute.dev/kyle/sift/internal/search/dial"
+)
+
+func TestLoopbackAllowsConfiguredPort(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(200)
+		_, _ = w.Write([]byte("ok"))
+	}))
+	defer ts.Close()
+	c, err := dial.New(ts.URL, dial.Options{Loopback: true, Timeout: 0})
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp, err := c.HTTP.Get(ts.URL + "/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		t.Fatalf("status %d", resp.StatusCode)
+	}
+}
+
+func TestLoopbackRefusesOtherPort(t *testing.T) {
+	c, err := dial.New("http://127.0.0.1:8888", dial.Options{
+		Loopback: true,
+		Lookup: func(_ context.Context, _ string) ([]netip.Addr, error) {
+			return []netip.Addr{netip.MustParseAddr("127.0.0.1")}, nil
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp, err := c.HTTP.Get("http://127.0.0.1:11434/")
+	if err == nil {
+		resp.Body.Close()
+		t.Fatal("dialed other loopback port")
+	}
+	if !strings.Contains(err.Error(), "refused") && !strings.Contains(err.Error(), "search dial") {
+		t.Fatalf("err %v", err)
+	}
+}
+
+func TestPublicPoisonedPrivateRefused(t *testing.T) {
+	_, err := dial.New("https://api.tavily.com/search", dial.Options{
+		Loopback: false,
+		Lookup: func(_ context.Context, host string) ([]netip.Addr, error) {
+			return []netip.Addr{netip.MustParseAddr("127.0.0.1")}, nil
+		},
+	})
+	if err == nil {
+		t.Fatal("poisoned A record allowed")
+	}
+}
+
+func TestPublicPrivateRFC1918Refused(t *testing.T) {
+	_, err := dial.New("https://api.search.brave.com/res/v1/llm/context", dial.Options{
+		Lookup: func(_ context.Context, _ string) ([]netip.Addr, error) {
+			return []netip.Addr{netip.MustParseAddr("10.0.0.5")}, nil
+		},
+	})
+	if err == nil {
+		t.Fatal("private A allowed")
+	}
+}
+
+func TestTLSSystemRoots(t *testing.T) {
+	c, err := dial.New("https://api.tavily.com/search", dial.Options{
+		Lookup: func(_ context.Context, _ string) ([]netip.Addr, error) {
+			return []netip.Addr{netip.MustParseAddr("1.1.1.1")}, nil
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	cfg := c.TLSConfig()
+	if cfg == nil {
+		t.Fatal("nil tls")
+	}
+	if cfg.InsecureSkipVerify {
+		t.Fatal("InsecureSkipVerify")
+	}
+	if cfg.RootCAs != nil {
+		t.Fatal("want system roots (nil RootCAs)")
+	}
+}
+
+func TestNoUserinfo(t *testing.T) {
+	_, err := dial.New("http://u:p@127.0.0.1:8888", dial.Options{Loopback: true})
+	if err == nil {
+		t.Fatal("userinfo allowed")
+	}
+}
+
+func TestParseRejectsNonHTTP(t *testing.T) {
+	_, err := dial.New("ftp://example.com/", dial.Options{})
+	if err == nil {
+		t.Fatal("ftp allowed")
+	}
+	_ = url.URL{}
+}