* fix(stream): preserve fade nodes while prose is live
* fix(stream): preserve transparent fade nodes like assistant prose
The transparent-activity prose path (transparent_stream mode) kept the
pre-PR fade cleanup: _bindTransparentFadeCleanup() in static/ui.js still
replaced every animated stream-fade-word span with a fresh text node on
animationend, invalidating the native scroll anchor while the row is
still growing.
Mirror the messages.js fix so both live prose paths share one
node-preserving cleanup: remove only the transient is-new class and the
--stream-fade-ms inline property, keeping span identity until final
settlement rebuilds the persisted DOM.
Extend tests/test_smooth_text_fade.py with a sibling regression that
extracts the production _bindTransparentFadeCleanup() from ui.js and
fires animationend, asserting no replacement, is-new removal,
stream-fade-word retention, and timing-override cleanup (plus
source-string guards against replaceWith in the cleanup block). The new
test is red-before-green against the previous ui.js implementation.
* docs(changelog): stamp #6257 (stream fade scroll-bounce fix)
---------
Co-authored-by: Anthony Ruiz <ruizanthony@users.noreply.github.com>
Co-authored-by: nesquena-hermes <nesquena-hermes@users.noreply.github.com>
