Gate findings (Codex 2-CORE / Opus SHIP-WITH-FIXES), both fixed:
1. cross-profile leak — _pre_compression_continuation_session_id scanned all profiles' sessions,
matched only by parent_session_id; now filters children by _profiles_match(child, snapshot)
+ validates returned sid with is_safe_session_id. +cross-profile regression test.
2. restore-state poison — frontend wrote continuationSid to localStorage/URL BEFORE the inner
loadSession proved it loadable; removed the speculative write (success path at the loaded id
handles it). Updated the source-grep test to assert the safe form.
Bounded BFS (range(20)+seen) + recursion guard confirmed safe by both gates.