v0.51.835 — remove transparent-stream live-row entrance animation

Fixed

• Transparent Stream: removed the last source of live-row flicker during streaming. After the identity-reconcile fix (#5400), some users still saw the live response area blink while the assistant was responding, because live rows that rebuilt outside the stable-key path replayed the row entrance animation. The transparent-event-row entrance animation (and its now-unused @keyframes) has been removed entirely, so rebuilds no longer replay an entrance shimmer. The graduated data-transparent-fade depth-fade (older rows dimming) is fully preserved. Thanks @rodboev. (#5454, #5367)

Full gate: Codex SAFE + Opus SHIP + CI (15 shards × py3.11/3.12/3.13) + activity-stream regression gate & browser matrix (14/14 checkpoints, both modes) + live reload-drive.