docs: refine live session timing motion rule

Author: linhay

.agents/skills/gettokens-domain-engineering/SKILL.md

@@ -160,6 +160,7 @@ This skill unifies the technical rules for building, styling, and debugging GetT
   - Trend chart viewport should be a fixed, non-scrollable heartbeat strip chart. Keep a stable time density with the latest request anchored near the right edge: wider surfaces can reveal more of the recent window, narrower surfaces show fewer recent samples. Do not reintroduce horizontal panning or auto-scroll follow logic.
   - Keep the live-session chart visually inside the page section, not as a nested card. Use the existing Swiss-industrial chart tokens, footer summaries below the graph, and live markers such as dashed strokes/rings for in-flight samples.
   - Request timing trend visuals should read closer to an ECG / request heartbeat than a smooth finance area chart. Keep the data-driven timestamp x-axis and metric values, but render the selected timing metric as angular pulse segments with no filled area; use stroke weight, opacity, color, and live rings to distinguish the active metric from the others.
+  - Timing trend motion should not redraw the full strip on every live refresh. Keep the line steady; use a short opacity settle only when switching metrics and a subtle breathing ring on the live sample to indicate activity.
   - The request timeline inside the detail pane is a recent-scan surface, not the full history list. Render only the latest 15 sorted request rows and keep the visible row count aligned with that cap; rely on history/detail data for deeper inspection.
   - Browser preview data for timing charts must include multiple completed requests plus one in-flight request, so `#frame=codex&workspace=live-sessions` exercises curve shape, latest sample footer, and live marker behavior without a Wails runtime.
   - Regression coverage for this class should include pure trend model tests, source-structure tests for live refresh / timestamp x-axis, preview multi-sample assertions, `typecheck`, `build`, focused `model.test.mjs`, and at least one browser/DevTools DOM or screenshot check that the chart renders nonblank.