fix(ui): prevent text clipping in execution overview state history

[sanjay78632]

✨ Description

Fixes text clipping in the Execution Overview page's State History timeline when the left panel is too narrow.

The root cause was el-timeline-item's :timestamp prop which renders timestamps using position: absolute; left: -210px. When the panel is narrower than ~210px, these timestamps are pushed outside the visible area and clipped by parent overflow: hidden — with no way to scroll to them.

Fix: Removed the :timestamp prop and moved both the timestamp and state name into the content slot using a flex layout (.timeline-row). Since they are now in normal document flow, they can never be clipped — and on very narrow panels they wrap gracefully onto separate lines.

🔗 Related Issue

Closes #14878.

🎨 Frontend Checklist

• Code builds without errors (npm run build)
• All existing E2E tests pass (npm run test:e2e)
• Screenshots or video recordings attached showing the UI changes

📝 Additional Notes

Only one file changed: ui/src/components/executions/overview/components/sidebar/Timeline.vue

• Removed :timestamp prop from el-timeline-item
• Added .timeline-row flex container inside the content slot
• Removed now-unused .el-timeline-item__timestamp absolute positioning styles

screen-recording-1772868215264.mp4