applyBatch rebuilt the strategy's agent summary after every accepted agent
element op, reading every agent element of the strategy across all its
pages. Most agent ops are moves, which can't change the summary: on a
20-page strategy one agent drag read 75 KB, against 4.6 KB for any other
element. Compare what the row adds to the summary (agent type and page,
while live) before and after the op, and rebuild only when that changed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>