Guard plugin selection refresh during config reload

[gernotmuc]

Summary

• suppress plugin-driven selection refresh while a plugin configuration change reloads the current log
• • clear the live selection before forcing the reload path
• • rebuild plugin state through the normal log reload flow after config changes

Notes

• public port of the validated internal viewer-side fix

[gernotmuc]

This slice is superseded by the additive restack:

• core/base PR: Improve viewer core stability and search performance #818
• filter follow-up: Improve filter loading and predecode handling gernotmuc/dlt-viewer#9

The goal is that each PR state builds on its own and the next layer applies on top instead of acting as an alternative. Closing this older parallel PR to keep the review path focused on the stacked pair.