feat(10-07): add Replit and CodeSandbox scraping sources

- ReplitSource scrapes /search HTML extracting /@user/repl anchors
- CodeSandboxSource scrapes /search HTML extracting /s/slug anchors
- Both use golang.org/x/net/html parser, 10 req/min rate, RespectsRobots=true
- 10 httptest-backed tests covering extraction, ctx cancel, rate/name assertions

pkg/recon/sources/codesandbox.go

@@ -0,0 +1,95 @@
+package sources
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/url"
+	"regexp"
+	"time"
+
+	"golang.org/x/time/rate"
+
+	"github.com/salvacybersec/keyhunter/pkg/providers"
+	"github.com/salvacybersec/keyhunter/pkg/recon"
+)
+
+// CodeSandboxSource scrapes codesandbox.io search results for references to
+// provider keywords. Mirrors ReplitSource: robots-respecting, 10 req/min,
+// no credentials required.
+type CodeSandboxSource struct {
+	BaseURL  string
+	Registry *providers.Registry
+	Limiters *recon.LimiterRegistry
+	Client   *Client
+}
+
+// codeSandboxLinkRE matches /s/<slug> sandbox result links.
+var codeSandboxLinkRE = regexp.MustCompile(`^/s/[a-zA-Z0-9-]+$`)
+
+// Compile-time assertion that CodeSandboxSource satisfies recon.ReconSource.
+var _ recon.ReconSource = (*CodeSandboxSource)(nil)
+
+func (s *CodeSandboxSource) Name() string                 { return "codesandbox" }
+func (s *CodeSandboxSource) RateLimit() rate.Limit        { return rate.Every(6 * time.Second) }
+func (s *CodeSandboxSource) Burst() int                   { return 1 }
+func (s *CodeSandboxSource) RespectsRobots() bool         { return true }
+func (s *CodeSandboxSource) Enabled(_ recon.Config) bool  { return true }
+
+// Sweep runs a CodeSandbox search per provider keyword and emits one Finding
+// per matched result anchor.
+func (s *CodeSandboxSource) Sweep(ctx context.Context, _ string, out chan<- recon.Finding) error {
+	base := s.BaseURL
+	if base == "" {
+		base = "https://codesandbox.io"
+	}
+	client := s.Client
+	if client == nil {
+		client = NewClient()
+	}
+
+	queries := BuildQueries(s.Registry, "codesandbox")
+	if len(queries) == 0 {
+		return nil
+	}
+
+	for _, q := range queries {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+
+		if s.Limiters != nil {
+			if err := s.Limiters.Wait(ctx, s.Name(), s.RateLimit(), s.Burst(), false); err != nil {
+				return err
+			}
+		}
+
+		searchURL := fmt.Sprintf("%s/search?query=%s&type=sandboxes", base, url.QueryEscape(q))
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, searchURL, nil)
+		if err != nil {
+			return fmt.Errorf("codesandbox: build req: %w", err)
+		}
+		resp, err := client.Do(ctx, req)
+		if err != nil {
+			return fmt.Errorf("codesandbox: fetch: %w", err)
+		}
+		links, err := extractAnchorHrefs(resp.Body, codeSandboxLinkRE)
+		_ = resp.Body.Close()
+		if err != nil {
+			return fmt.Errorf("codesandbox: parse html: %w", err)
+		}
+
+		for _, href := range links {
+			if err := ctx.Err(); err != nil {
+				return err
+			}
+			out <- recon.Finding{
+				Source:     base + href,
+				SourceType: "recon:codesandbox",
+				Confidence: "low",
+				DetectedAt: time.Now(),
+			}
+		}
+	}
+	return nil
+}