feat(11-01): add DuckDuckGoSource, YandexSource, and BraveSource

- DuckDuckGoSource scrapes HTML search (no API key, always enabled, RespectsRobots=true)
- YandexSource uses Yandex XML Search API (user+key required, XML response parsing)
- BraveSource uses Brave Search API (X-Subscription-Token header, JSON response)
- All three follow established error handling: 401 aborts, transient continues, ctx cancellation returns

pkg/recon/sources/yandex_test.go

@@ -0,0 +1,171 @@
+package sources
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"github.com/salvacybersec/keyhunter/pkg/recon"
+)
+
+const yandexXMLFixture = `<?xml version="1.0" encoding="utf-8"?>
+<yandexsearch>
+  <response>
+    <results>
+      <grouping>
+        <group>
+          <doc>
+            <url>https://pastebin.com/yandex1</url>
+          </doc>
+        </group>
+        <group>
+          <doc>
+            <url>https://github.com/user/repo/blob/main/secrets.env</url>
+          </doc>
+          <doc>
+            <url>https://example.com/leaked</url>
+          </doc>
+        </group>
+      </grouping>
+    </results>
+  </response>
+</yandexsearch>`
+
+func yandexStubHandler(t *testing.T, calls *int32) http.HandlerFunc {
+	t.Helper()
+	return func(w http.ResponseWriter, r *http.Request) {
+		atomic.AddInt32(calls, 1)
+		if !strings.HasPrefix(r.URL.Path, "/search/xml") {
+			t.Errorf("unexpected path: %s", r.URL.Path)
+		}
+		if r.URL.Query().Get("user") != "testuser" {
+			t.Errorf("missing user param")
+		}
+		if r.URL.Query().Get("key") != "testkey" {
+			t.Errorf("missing key param")
+		}
+		w.Header().Set("Content-Type", "application/xml")
+		_, _ = w.Write([]byte(yandexXMLFixture))
+	}
+}
+
+func TestYandexSource_EnabledRequiresBoth(t *testing.T) {
+	reg := syntheticRegistry()
+	lim := recon.NewLimiterRegistry()
+
+	tests := []struct {
+		user, key string
+		want      bool
+	}{
+		{"", "", false},
+		{"user", "", false},
+		{"", "key", false},
+		{"user", "key", true},
+	}
+	for _, tt := range tests {
+		s := NewYandexSource(tt.user, tt.key, reg, lim)
+		if got := s.Enabled(recon.Config{}); got != tt.want {
+			t.Errorf("Enabled(user=%q, key=%q) = %v, want %v", tt.user, tt.key, got, tt.want)
+		}
+	}
+}
+
+func TestYandexSource_SweepEmptyCredsReturnsNil(t *testing.T) {
+	reg := syntheticRegistry()
+	lim := recon.NewLimiterRegistry()
+	s := NewYandexSource("", "", reg, lim)
+
+	out := make(chan recon.Finding, 10)
+	if err := s.Sweep(context.Background(), "", out); err != nil {
+		t.Fatalf("expected nil, got %v", err)
+	}
+	close(out)
+	if n := countFindings(out); n != 0 {
+		t.Fatalf("expected 0 findings, got %d", n)
+	}
+}
+
+func TestYandexSource_SweepEmitsFindings(t *testing.T) {
+	reg := syntheticRegistry()
+	lim := recon.NewLimiterRegistry()
+	_ = lim.For("yandex", 1000, 100)
+
+	var calls int32
+	srv := httptest.NewServer(yandexStubHandler(t, &calls))
+	defer srv.Close()
+
+	s := NewYandexSource("testuser", "testkey", reg, lim)
+	s.BaseURL = srv.URL
+
+	out := make(chan recon.Finding, 32)
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	done := make(chan error, 1)
+	go func() { done <- s.Sweep(ctx, "", out); close(out) }()
+
+	var findings []recon.Finding
+	for f := range out {
+		findings = append(findings, f)
+	}
+	if err := <-done; err != nil {
+		t.Fatalf("Sweep error: %v", err)
+	}
+
+	// 2 keywords * 3 URLs in XML = 6 findings
+	if len(findings) != 6 {
+		t.Fatalf("expected 6 findings, got %d", len(findings))
+	}
+	for _, f := range findings {
+		if f.SourceType != "recon:yandex" {
+			t.Errorf("SourceType=%q want recon:yandex", f.SourceType)
+		}
+	}
+	if got := atomic.LoadInt32(&calls); got != 2 {
+		t.Errorf("expected 2 calls, got %d", got)
+	}
+}
+
+func TestYandexSource_CtxCancelled(t *testing.T) {
+	reg := syntheticRegistry()
+	lim := recon.NewLimiterRegistry()
+	_ = lim.For("yandex", 1000, 100)
+
+	s := NewYandexSource("user", "key", reg, lim)
+	s.BaseURL = "http://127.0.0.1:1"
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	out := make(chan recon.Finding, 1)
+	err := s.Sweep(ctx, "", out)
+	if !errors.Is(err, context.Canceled) {
+		t.Fatalf("expected context.Canceled, got %v", err)
+	}
+}
+
+func TestYandexSource_Unauthorized(t *testing.T) {
+	reg := syntheticRegistry()
+	lim := recon.NewLimiterRegistry()
+	_ = lim.For("yandex", 1000, 100)
+
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusUnauthorized)
+		_, _ = w.Write([]byte("bad creds"))
+	}))
+	defer srv.Close()
+
+	s := NewYandexSource("user", "key", reg, lim)
+	s.BaseURL = srv.URL
+
+	out := make(chan recon.Finding, 1)
+	err := s.Sweep(context.Background(), "", out)
+	if !errors.Is(err, ErrUnauthorized) {
+		t.Fatalf("expected ErrUnauthorized, got %v", err)
+	}
+}