Corpus: stored XOVER chunks for the grouping sweeps

Ranges marked `capture` keep their XOVER chunks in CORPUS_DIR
(corpus/<group>/<start>-<end>/, edge-bench's layout, range.json once
complete; only chunks that inflate). The prefetcher reads a stored chunk
instead of fetching it, so a reset re-indexes them without the news
server; a chunk a worker reports corrupt goes from the corpus too.

edge-bench gets --releases (release chunks without payload, with their
first subjects) and ships in the edge image; deploy/corpus_sweep.py marks
more ranges (capture), replays the corpus with the deployed build (replay)
and reports suspects and the change since the previous build (report).

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

deploy/README.md

@@ -34,6 +34,8 @@ homelab with the deploy key, whose forced command
 | `src/` | the code at the deployed commit (the build context) |
 | `pg/` | Postgres data (HDD) |
 | `spool/` | prefetched XOVER chunks |
+| `corpus/` | stored XOVER chunks of ranges marked `capture`, for the grouping sweeps (up to 300 GB) |
+| `corpus-out/` | the sweeps' replays, per edge image (`python3 src/deploy/corpus_sweep.py`) |
 | `deployed.log` | one line per deploy: sha, time (local) |
 | `.cache/repo.git` | bare clone the deploys fetch into |
 | `app/` | an older copy of the code with dev dependencies, for `tools/*.ts` (`r.sh`); not what runs |