fix(metrics): skip unanchored step-metrics — no more empty bubbles at tail

Step-metrics are only shown when anchored to their tool content (inline
after the tool-call/result group). Steps whose chunks were trimmed (or
text-only steps with no tool chunks) are now SKIPPED instead of piling
up at the segment tail as empty 'step N · X tok' bubbles.

The turn-total metrics row still shows the aggregate (tokens, duration,
cache rate), so the conversation-level summary is preserved.

Updated place.test.ts + ui.test.ts to anchor steps with tool-call groups
where step-metrics are expected.

0 files changed, 0 insertions, 0 deletions