fix(story-mode): one turn per prompt written twice, and plan mode as planning

From review round 3 (compaction, then plan mode):

- A typed `/compact` and its <command-name> record share one promptId; they
  were two turns ("Done in 0 seconds", then a turn left running). A prompt
  carrying the open turn's promptId now joins it: one "You run /compact."
  turn of 24 s, the real compaction time. A command typed as such
  (`/model opus`) is a command too.
- Plan mode: writing the plan file under ~/.claude/plans/ is planning (a plan
  panel with its numbered steps), not a code change ("3 files changed" for
  a commit of 2). ExitPlanMode's input is empty in current builds; its
  result carries the plan and your answer: "Claude shows you its plan, and
  you approve it."
- A command's Director's caption names it ("Command · /compact").

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

docs/api-reference.md

@@ -1067,7 +1067,7 @@ Responses carry a weak `ETag` with `Cache-Control: no-cache`; a request with a m
 
 A `page` carries the turn's summary fields plus `events` (one per prompt, sentence Claude wrote and tool call, with `intent`, `ok` when the call returned, `edit` hunks in Claude Code's own `structuredPatch` shape, the tail of `output`, `helper`, `tests` counts, and `files` for the files a Bash call printed with `cat`/`head`/`tail`, as the command named them), `panels` (each `{ kind, events, caption: { story, director }, balloon?, files?, ... }`, at most 12 per page, indices into `events`), `filesChanged`, `added`, `removed`, `helpers`, `helpersRunning`, `partial` (the turn began before the part that was read) and `truncated` (older outputs were dropped to keep the page small). A transcript that cannot be read is a `500` with `OPERATION_FAILED`.
 
-A helper started in the background (`helper.background`) carries `helper.running: true` until its `<task-notification>` arrives; that notification starts a turn of its own (origin `task`), whose prompt event carries the helper's answer as `output`, and the answer, tool count and duration are joined back onto the helper in the turn that started it. Claude Code times such a turn from the prompt that started the chain; Story Mode caps a turn's `durationMs` at the turn's own span. A helper started as a teammate (`status: teammate_spawned`) is a background helper too, and its `<teammate-message>` reports join it by name. A prompt that arrives while Claude works (typed, a background job's report, a message from another session) is written by current Claude Code builds as a `queued_command` attachment, not a user line; it joins the running turn, a prompt event carrying `origin` (`human`, `task`, `peer`, `system`), and a report that lands mid-turn is an event with intent `notice` rather than a new mission panel. A Bash call that writes files through here-documents (`cat > f <<'EOF'`) carries them as `edits` (whole-file edits, counted in `filesChanged`), and its label leaves the bodies out; `headline` is the part of a one-liner that decided its intent. The advisor (a server tool) is an event with tool `Advisor` and intent `helper`; its answer is encrypted in the transcript. `tests` may carry `errors` (pytest's collection errors). A slash command is a prompt event with tool `Command`; a local one (`/compact`, `/model`) ends its turn at its own output (`<local-command-stdout>`, kept as the event's `output`), and a compaction that lands between turns belongs to the turn after it. A turn ends at `turn_duration`, or at the Stop hook's `stop_hook_summary` (unless it prevented the stop) in sessions that never write `turn_duration`, timed then by its own span.
+A helper started in the background (`helper.background`) carries `helper.running: true` until its `<task-notification>` arrives; that notification starts a turn of its own (origin `task`), whose prompt event carries the helper's answer as `output`, and the answer, tool count and duration are joined back onto the helper in the turn that started it. Claude Code times such a turn from the prompt that started the chain; Story Mode caps a turn's `durationMs` at the turn's own span. A helper started as a teammate (`status: teammate_spawned`) is a background helper too, and its `<teammate-message>` reports join it by name. A prompt that arrives while Claude works (typed, a background job's report, a message from another session) is written by current Claude Code builds as a `queued_command` attachment, not a user line; it joins the running turn, a prompt event carrying `origin` (`human`, `task`, `peer`, `system`), and a report that lands mid-turn is an event with intent `notice` rather than a new mission panel. A Bash call that writes files through here-documents (`cat > f <<'EOF'`) carries them as `edits` (whole-file edits, counted in `filesChanged`), and its label leaves the bodies out; `headline` is the part of a one-liner that decided its intent. The advisor (a server tool) is an event with tool `Advisor` and intent `helper`; its answer is encrypted in the transcript. `tests` may carry `errors` (pytest's collection errors). A prompt written twice under one `promptId` (a typed `/compact`, then its command record) is one turn. In plan mode the plan file under `~/.claude/plans/` is planning (intent `plan`, its numbered steps as `todos`), not a code change, and `ExitPlanMode`'s result carries the plan (the event's `output`) and your answer (`Approved` / `Sent back`). A slash command is a prompt event with tool `Command`; a local one (`/compact`, `/model`) ends its turn at its own output (`<local-command-stdout>`, kept as the event's `output`), and a compaction that lands between turns belongs to the turn after it. A turn ends at `turn_duration`, or at the Stop hook's `stop_hook_summary` (unless it prevented the stop) in sessions that never write `turn_duration`, timed then by its own span.
 
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