Function run_paging_loop_shared 

pub fn run_paging_loop_shared<T: Read + Write, A: SlotArena, S: SwapStore>(
    stream: &mut T,
    res: &Mutex<Residency<A, S>>,
) -> Result<()>

2026-09-25: run_paging_loop over a residency shared by many connections, so a blob one client PUTs another can GET under the same key. The lock is held for each dispatch, which may move bytes to or from swap, and never across a TCP read or write.