PR Notes: Opt-in Smooth Streaming Text Fade

Summary

Adds an opt-in Fade text effect preference for live assistant responses. When enabled, newly revealed words fade in during streaming for a smoother ChatGPT/Codex-like feel while preserving the existing default streaming path when disabled.

User-facing behavior

New setting: Settings -> Preferences -> Fade text effect
Default: off
Runtime flag: window._fadeTextEffect
Fade mode uses a playout buffer so fast backend chunks do not land as large paragraph pops.
Visual reveal rate is intentionally capped for readability, especially with very fast models.
Live cursor is hidden while fade mode is active.
Reduced-motion users get non-animated text.

Implementation notes

Fade mode is locked per stream to avoid mid-stream preference toggle rewind/duplication.
Uses Hermes' existing incremental streaming-markdown parser with a custom renderer instead of full markdown re-renders.
Only newly appended words are wrapped and animated.
Animated spans are replaced with plain text by a delegated animationend handler, avoiding long-lived wrapper buildup without per-word listeners.
Reduced-motion preference is cached with a media-query listener instead of checked for every appended text node.
Unsafe streamed href/src values are blocked in the fade renderer set_attr path.
On done, fade mode drains buffered text, ends the parser to flush pending markdown, and waits for the final fade/stagger window before the final renderMessages() replacement.

Performance/readability tuning

Normal fade duration: 160ms
Word stagger: 12ms
Done drain wait cap: 220ms
Visual playback is capped at 100 wps.
Reveals at most 2 words/frame, or 3 words/frame only with very large backlog.
Reveal steps pause briefly after sentence punctuation and paragraph breaks so very fast models feel less overwhelming.
Target word counts reuse the already-visible word count plus backlog count, avoiding repeated full-response word scans on each tick.

Verification

node --check static/messages.js static/panels.js static/boot.js static/i18n.js
git diff --check
/Users/agent/.hermes/hermes-agent/venv/bin/python -m pytest tests/test_smooth_text_fade.py tests/test_1003_preferences_autosave.py tests/test_streaming_markdown.py -q
/Users/agent/.hermes/hermes-agent/venv/bin/python -m py_compile api/config.py

Latest focused result:

68 passed

Manual QA suggested

Hard refresh after deployment.
Enable Settings -> Preferences -> Fade text effect.
Test short normal response.
Test long markdown response with headings, lists, links, code blocks, and tables.
Test very fast model output around 200-400 tok/s.
Test tool-call-heavy response.
Test OS/browser reduced-motion mode if available.

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