Say what each button does, and allow filming again after an edit

Three things were unclear or missing:

- "Make the frame" reads as though it might film the shot. It draws one still,
  the opening frame, and films nothing. Say so.
- Once a project was ready there was no way to film it again, so editing a
  shot afterwards led nowhere. The film card now appears for a finished video
  as "Film it again".
- Nothing explained that these per-shot buttons are optional. Filming draws
  any missing frame and makes any missing cutaway itself, so they are there to
  preview, not to complete.

script.html

@@ -124,7 +124,9 @@ function shotHtml(s, locked) {
     + '<div>' + picker + '</div>'
     + '<div style="display:flex;align-items:flex-end">'
     + '<button type="button" class="btn ghost" data-make="' + s.index + '" style="width:100%">'
-    + (s.plate_url ? "Remake this frame" : "Make the frame") + '</button></div>'
+    + (s.plate_url ? "Redraw the opening still" : "Draw the opening still") + '</button>'
+    + '<span class="foot" style="display:block;margin-top:6px">One picture, not the video. '
+    + 'It is drawn from their photo and is what carries their likeness.</span></div>'
     + '</div>';
 
   return '<div class="shot">'
@@ -203,7 +205,8 @@ function render(r) {
   // Filming, from the browser. This was the last step that needed an operator.
   var film = '';
   if (p.status === 'approved' || p.status === 'queued_to_film'
-      || p.status === 'filming' || p.status === 'film_failed') {
+      || p.status === 'filming' || p.status === 'film_failed'
+      || p.status === 'ready') {
     var busy = (p.status === 'queued_to_film' || p.status === 'filming');
     // The opening frame is what carries the animal's likeness into the video.
     // Without one the model works from the written description and invents a
@@ -231,9 +234,16 @@ function render(r) {
       + (busy
           ? '<p class="foot" id="filmnote">' + esc(p.film_note || 'Queued…') + '</p>'
           : '<button type="button" class="btn" id="film">'
-            + (p.status === 'film_failed' ? 'Try filming again' : 'Film it')
+            + (p.status === 'film_failed' ? 'Try filming again'
+               : (p.status === 'ready' ? 'Film it again' : 'Film it'))
             + '</button>'
-            + '<span class="foot" style="margin-left:12px">About a minute a shot.</span>')
+            + '<span class="foot" style="margin-left:12px">About a minute a shot. '
+            + 'Anything still missing — an opening still, a cutaway — is made '
+            + 'automatically first, so nothing above is required.</span>'
+            + (p.status === 'ready'
+                ? '<p class="foot" style="margin:10px 0 0">This has already been filmed. '
+                  + 'Filming again spends the seconds again and replaces the video.</p>'
+                : ''))
       + '</div>';
   }