fix(panel): drop stale hover when meter leaves rendered set

Visibility rules can filter a hovered meter out of compactProviders()
while its provider stays in the roster, and its destroyed MouseArea
delivers no reliable hover-exit. Narrow the tooltip only while the
hovered meter is actually rendered, and clear the stale hover when the
rendered meter set changes.

Addresses CodeRabbit review on PR #205.
80c6a9d47cSimone committed on 9/10/2026, 2:58:04 PMparentb7e7809

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