feat(inspect): serveHTML route under /api/runs/<id>/html/<name>

Mirrors serveScreenshot path validation; rejects traversal segments and
unknown extensions. text/html content-type so the iframe renders cleanly.

internal/inspect/server.go

@@ -84,6 +84,7 @@ func (s *Server) handleRunsList(responseWriter http.ResponseWriter, request *htt
 
 var stepPathPattern = regexp.MustCompile(`^([a-zA-Z0-9._-]+)/steps/([^/]+)$`)
 var screenshotPathPattern = regexp.MustCompile(`^([a-zA-Z0-9._-]+)/screenshots/([a-zA-Z0-9._-]+\.png)$`)
+var htmlPathPattern = regexp.MustCompile(`^([a-zA-Z0-9._-]+)/html/([a-zA-Z0-9._-]+\.html)$`)
 var runDetailPathPattern = regexp.MustCompile(`^([a-zA-Z0-9._-]+)/?$`)
 
 func (s *Server) handleRunsTree(responseWriter http.ResponseWriter, request *http.Request) {
@@ -104,6 +105,10 @@ func (s *Server) handleRunsTree(responseWriter http.ResponseWriter, request *htt
 		s.serveScreenshot(responseWriter, request, match[1], match[2])
 		return
 	}
+	if match := htmlPathPattern.FindStringSubmatch(rest); match != nil {
+		s.serveHTML(responseWriter, request, match[1], match[2])
+		return
+	}
 	if match := runDetailPathPattern.FindStringSubmatch(rest); match != nil {
 		s.serveDetail(responseWriter, match[1])
 		return
@@ -160,6 +165,20 @@ func (s *Server) serveScreenshot(responseWriter http.ResponseWriter, request *ht
 	http.ServeFile(responseWriter, request, full)
 }
 
+func (s *Server) serveHTML(responseWriter http.ResponseWriter, request *http.Request, id, name string) {
+	if !validRunID(id) || strings.Contains(name, "..") {
+		http.Error(responseWriter, "run not found", http.StatusNotFound)
+		return
+	}
+	full := filepath.Join(s.options.RunsDirectory, id, "html", name)
+	if _, err := http.Dir(filepath.Join(s.options.RunsDirectory, id, "html")).Open(name); err != nil {
+		http.NotFound(responseWriter, request)
+		return
+	}
+	responseWriter.Header().Set("Content-Type", "text/html; charset=utf-8")
+	http.ServeFile(responseWriter, request, full)
+}
+
 func (s *Server) handleEvents(responseWriter http.ResponseWriter, request *http.Request) {
 	flusher, ok := responseWriter.(http.Flusher)
 	if !ok {