ChatModel.load_history rebuilds the resumed session so the chat renders the
same way as a live turn:

- Recover tool-call args via tool_call_id (the persisted tool message stores
  only the result, not the call args) and forward the stored metadata. Without
  this the filesystem renderer saw args={} -> action=None and fell back to a
  plain, un-highlighted result -- the resume "no syntax highlighting" symptom.
- Emit assistant_message BEFORE tool_started when an assistant message has both
  text and tool_calls, matching the live stream where stream_delta precedes
  tool_started; previously the answer was stranded under its own tool cards.
- Append a turn_meta item when the persisted assistant message carries
  elapsed_seconds, reproducing the single duration line stream_end appends.

is_subagent for resumed tool calls is intentionally deferred (needs storage).