* test(popup): cover header tooltip hover, status target, and usage docs

Follow-up to #397: document the provider header tooltip behavior in the
maintained usage guide, assert hover show/hide plus the untruncated
negative case in the header test, and pin the status hover target to the
full badge slot with a new visual-layout test.

* test(popup): widen header for the fitted-label negative case

At 200px the fixed chrome (icon, Refresh button) can squeeze the meta
row below the short labels' implicit width on some font metrics (CI:
account label 16px wide vs 41px implicit), leaving them truncated and
failing the negative case. Widen to 600px before swapping in short data
so fitted labels genuinely fit.