The settled current-summary card was only created when no compaction
marker was loaded at all. A transcript with older (stale) markers plus a
newer `compression_anchor_summary` that no loaded marker references
therefore lost the current summary, which master still rendered.
Decide the fallback from `_latestCompressionReferenceMessage()`
(`referenceMessageRawIdx < 0`) instead of marker presence, and feed that
decision into `_selectCompactionCardPlacements()` before any card node is
built so the fallback is the single preserved-task owner and marker cards
never attach the task list a second time.
Add a render-level regression that executes the real `renderMessages()`
over 220 messages, three stale markers, one preserved task-list message
and a newer summary: the current summary is visible and exactly one task
owner is rendered, in full, virtualized and server-truncated windows.
