Codex round-3 gate finding: _dedupe_replayed_context_messages deep-copies the
stale-user repaired boundary row (streaming.py:4501) into the context array. When
the mint ran AFTER dedupe, that deep-copied context row was no longer the shared
result dict, so it stayed id-less while the display copy got the minted id —
re-opening the cross-array id divergence for the stale-repair path. Fix: move
_assign_stable_message_ids() to run immediately after _restore_reasoning_metadata
and BEFORE _dedupe_replayed_context_messages at all four commit sites (streaming
main / in-band self-heal / except-path self-heal + routes runs/MoA), so the shared
result rows are stamped before any deep-copy — both arrays inherit the id.