Extract the primary pane's per-screen enter/exit transition into a shared
`ScreenStage` element (the `fade-up` Mantine Transition: incoming screen slides
up + fades in while the outgoing fades down + out, both absolutely positioned).
InspectorView now imports it (behavior unchanged), and the pinned monitoring
column uses it too — via a new `fill` variant that stretches the stage to the
column's height — so switching Logs/Protocol/Network animates the same way as
switching the main screens.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BrihGWcrM9JGRyu41nzZYw