Keep web panels open after permission prompt actions

[aminought]

Choosing Allow or Block in a web panel's permission prompt also closes the floating web panel when Always on top is disabled. Firefox removes the notification before the click reaches the outer window, so the detached button fails the DOM containment check and is treated as an outside click.

Identify panel chrome through the button's owner document, which remains available after removal. This keeps the web panel open after a permission action and preserves dismissal on ordinary outside clicks.

Related to #193. The original report of unresponsive permission buttons has not been reproduced; this PR addresses the confirmed panel-closing behavior.

Validation:

• Firefox 155.0.1 on Windows in an isolated headless profile: reproduced closing before the change for both Allow and Block; verified their callbacks run, the prompt is removed, the panel stays open after the change, and outside clicks still close it. No FSS console errors.
• ESLint, Prettier on the changed file, and git diff --check pass.