Restores main's one-inset rule (#5226) that a rebase resolution had
overridden with a conditional right-2 offset, which made the controls jump
sideways whenever the right panel opened. Also restores the live-agent
count badge on the right-panel toggle (#5745) that the round-6 replay
dropped, and applies the same fixed-position rule to the pull requests
page: the toggle now stays mounted at one absolute inset in both states,
with a footprint spacer in the list header so the refresh button never
slides underneath it.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>