address review: reshape memory report and record unevictable reasons
- Group tasks by task type (including cell-less tasks) alongside the
existing cells-by-value-type breakdown; aggregate inside the parallel
per-shard loop rather than materializing a Vec of cell entries.
- Record why the last eviction couldn't reclaim each persistent task,
bucketed by UnevictableReason, per task type.
- Drop the sample dependency chains, the total-strong-count / distinct-
value-type fields, and the benchmark/visualize scripts.
- Type the dev-server markdown renderer instead of using `any`.