CoS tip: keep one row when a message is re-sent with the same id (#51033)

[kvnloo]

Origin

anomalyco#51033

Intent

When a live message.updated reuses an id at a new creation time, drop the stale row and insert at the new key instead of leaving duplicates in the session message list.

Proof (fail → pass)

cd packages/tui
bun test test/cli/cmd/tui/sync-live-hydration.test.tsx -t "a message re-sent with the same id keeps one row"
# NEGATIVE (base product + tip tests): 0 pass / 1 fail
# GREEN: 1 pass / 0 fail
# restore: 0 pass / 1 fail

Notes

• Base: dev
• github_writes_origin=0
• Codex promote: parked