The round-5 ChatView reconciliation kept the round-3-era PullRequestDetailPanel
call, so the panel mounted without chromeVariant="collapse" — the #6039
scroll-condensing chrome never engaged and the description scrolled under a
full-height chrome. Restore main's call exactly: collapse chrome,
composerDraftTarget for same-thread hand-offs, the isThreadOwnPullRequest
context check, and tab statuses keyed by the active surface id via
updatePullRequestTabStatus instead of a key rebuilt from the status payload.

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