Constant ROOM_PLACEMENT_TABLE 

pub const ROOM_PLACEMENT_TABLE: &'static str;

The room placement-fence table (RINDLE-REALTIME-DESIGN.md §2.5): one row per doc, bumped by every claim. A flush carrying an epoch below the current claim is fenced — validated with the apply on the single-threaded engine, so the check and the commit are atomic. Unregistered bookkeeping like SOURCE_OFFSETS_TABLE.