Line numbers are places in import and export; fix stale scripts

Import: each row's place is its line number, so blank lines leave a
place empty; a fully numbered text file ("38. Title") or a Rank column
gives places directly, and repeated numbers take the next free place.
Entries are added at those places (existing ones there move down), the
review shows each row's #, and the room check covers the highest place.

Export writes a blank line for every empty place, so line N is #N and a
file round-trips.

Static files now carry an ETag and unversioned ones are revalidated on
every load. Scripts import each other without a ?v= tag, so browsers kept
an hour-old import.js (with the "null" bug) after an update.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/server/export.go

@@ -14,8 +14,9 @@ var exportFormats = map[string]struct{ ext, contentType string }{
 	"txt": {"txt", "text/plain; charset=utf-8"},
 }
 
-// handleExport downloads a list's titles in rank order, one per line, with
-// nothing else: no ranks, header row or metadata.
+// handleExport downloads a list's titles, one per line, with nothing else:
+// no ranks, header row or metadata. Line N is place #N, so an empty place
+// is a blank line, and importing the file puts everything back where it was.
 func (s *Server) handleExport(w http.ResponseWriter, r *http.Request) {
 	format := r.URL.Query().Get("format")
 	if format == "" {
@@ -35,9 +36,12 @@ func (s *Server) handleExport(w http.ResponseWriter, r *http.Request) {
 		s.serverError(w, r, err)
 		return
 	}
-	titles := make([]string, len(items))
-	for i, it := range items {
-		titles[i] = it.Title
+	var titles []string
+	for _, it := range items {
+		for len(titles) < it.Rank-1 {
+			titles = append(titles, "")
+		}
+		titles = append(titles, it.Title)
 	}
 	w.Header().Set("Content-Type", f.contentType)
 	w.Header().Set("Content-Disposition", fmt.Sprintf(`attachment; filename="%s.%s"`, l.Slug, f.ext))

internal/server/server.go

@@ -321,20 +321,45 @@ func (s *Server) isHTTPS(r *http.Request) bool {
 
 func (s *Server) staticHandler() http.Handler {
 	fsrv := http.FileServerFS(s.static)
+	etags := staticETags(s.static)
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if strings.HasSuffix(r.URL.Path, "/") {
 			s.notFound(w, r)
 			return
 		}
+		if tag, ok := etags[strings.TrimPrefix(r.URL.Path, "/")]; ok {
+			w.Header().Set("ETag", tag) // FileServer answers If-None-Match with 304
+		}
 		if r.URL.Query().Get("v") != "" {
 			w.Header().Set("Cache-Control", "public, max-age=31536000, immutable")
 		} else {
-			w.Header().Set("Cache-Control", "public, max-age=3600")
+			// Scripts load each other without a ?v= (import "./places.js"),
+			// so unversioned files are re-checked on every load; the ETag
+			// makes that a quick 304 until a new build changes them.
+			w.Header().Set("Cache-Control", "no-cache")
 		}
 		fsrv.ServeHTTP(w, r)
 	})
 }
 
+// staticETags fingerprints every embedded static file once at startup.
+func staticETags(fsys fs.FS) map[string]string {
+	tags := map[string]string{}
+	fs.WalkDir(fsys, ".", func(p string, d fs.DirEntry, err error) error {
+		if err != nil || d.IsDir() {
+			return nil
+		}
+		b, err := fs.ReadFile(fsys, p)
+		if err != nil {
+			return nil
+		}
+		sum := sha256.Sum256(b)
+		tags[p] = `"` + hex.EncodeToString(sum[:8]) + `"`
+		return nil
+	})
+	return tags
+}
+
 func (s *Server) handleImage(w http.ResponseWriter, r *http.Request) {
 	name := r.PathValue("name")
 	if !imgcache.ValidName(name) {