fix(story-mode): scheduled runs, work after a turn ended, and pages full of added prompts

From review round 4 (a 110 MB real session, about 23 turns, read through
all four tail steps):

- A scheduled task's run was drawn inside the /compact turn before it (96
  minutes and 237 tool calls credited to "You run /compact."): its prompt is
  a meta line, and work after an ended turn was appended to that turn. The
  scheduled prompt now starts a turn of origin `scheduled` ("A scheduled
  task starts this turn."), and work that comes more than 5 s after a turn
  ended starts a turn of its own ("Claude carries on"); a line Claude Code
  flushed a moment late still joins.
- A turn with seven prompts added mid-turn drew 14 panels (the cap is 12):
  missions were never folded. An added prompt may now fold into a montage,
  as the last resort after quiet panels and work panels, and the montage
  says so ("Claude keeps going (you add 2 things): ..."); the turn's own
  prompt and a question to you are never folded.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/web/public/story-mode.js

@@ -1975,7 +1975,10 @@ Object.assign(CodemanApp.prototype, {
       ...turns.map((t, i) => {
         const o = document.createElement('option');
         o.value = t.id;
-        o.textContent = `${i + 1}. ${t.prompt || (t.origin === 'task' ? 'Background task' : 'Earlier work')}`;
+        o.textContent = `${i + 1}. ${
+          t.prompt ||
+          (t.origin === 'task' ? 'Background task' : t.origin === 'system' ? 'Claude carries on' : 'Earlier work')
+        }`;
         return o;
       })
     );