fix: pin DNS resolution against SSRF rebinding; enforce reviewer independence; bound caches and logs

- web.ts: outbound downloads resolve DNS once, validate the address, and
  connect to the validated IP directly, closing the DNS-rebinding TOCTOU
  window; malformed SearXNG result URLs are skipped instead of failing the
  whole search; web cache is bounded (evicts oldest past 500 entries).
- experiment.ts: reviewer must not be a descendant of the experiment author
  (tool-level lineage check on top of the author-id check); stdout/stderr
  buffers capped at 512 KB.
- Confirmed Pi's extension tool registry is per-extension-instance, so
  reload re-registration is safe; no change needed there.
- Adds a lineage-independence test (39 tests passing, tsc clean).

CHANGELOG.md

@@ -15,6 +15,17 @@
 - Full-text search now prefix-matches tokens (tolerates Russian/English
   inflections without stemming) and safely handles punctuation and FTS5
   metacharacters instead of throwing or returning false negatives.
+- Hardened the web gateway against SSRF TOCTOU: outbound downloads now resolve
+  DNS once, validate the address, and connect to the validated IP directly
+  (pinned resolution), so DNS rebinding cannot redirect the connection to a
+  private target; malformed search results no longer break the whole query;
+  the web cache is bounded (oldest entries evicted past 500 files).
+- Experiment review is now truly independent: the reviewer must not be a
+  descendant of the experiment author (in addition to not being the author).
+- Experiment stdout/stderr are capped at 512 KB so runaway container output
+  cannot exhaust memory or disk.
+- Verified that Pi's extension tool registry is per-extension-instance, so
+  reload re-registration is safe (no fix required).
 
 ## 0.1.1 — 2026-07-31