A red check's summary names each shard's first failure, never the (unnamed) fallout behind it #8730

Left open from #8679 (pull #8680, 0ea41d83): only the disk-full path names the first failure. Elsewhere, shards are logged in the order they finish, so a summary can lead with (unnamed) fallout or with a later shard's failure.

Done looks like:

• [x] For each red shard, the summary lists that shard's first named failure in output order. A (unnamed) entry shows only when the shard has no named failure.
• [x] Shards appear in shard order, not finish order.
• [x] Tests in the bun-test parser suite: a shard log with a named failure followed by unnamed fallout names the named one first; two shards that finish out of order are listed in shard order.

Files: src/checks/summary.ts, src/checks/bun-test.ts, src/checks/service.ts, a test beside them Risks: CheckJudgement.cause reads this summary, so environment faults must still be told apart as they are today.

Reviewed pull #8750 at its head: ticked For each red shard, the summary lists that shard's first named failure in output order. A (unnamed) entry shows only when the shard has no named failure.; Shards appear in shard order, not finish order.; Tests in the bun-test parser suite: a shard log with a named failure followed by unnamed fallout names the named one first; two shards that finish out of order are listed in shard order..