Re-running apply_scene_close_summary on the same scene previously caused
recursive bloat: _build_key_quotes_suffix sourced quote text from
memories.pov_summary, which after the first close already carried a
"Key quotes:" suffix. The next close would then quote the quotes,
nesting deeper each time.
Strip any existing suffix from candidate text before truncating to
200 chars in the suffix builder, and from the fresh classifier output
before composing the new value in _summarize_and_apply_for_witness so
the rewrite replaces rather than stacks.
Adds test_scene_close_re_run_does_not_double_suffix.
Joseph Doherty
d123684f9a