Function render_projected 

pub fn render_projected(
    partitions: &ContextPartitions,
    budget: u32,
    engine: &ContextTokenEngine,
    preserve_recent_units: usize,
    handles: &HandleTable,
    frozen_history_len: usize,
    collapse_narration: bool,
) -> RenderedContext

Render with Layer-4 read-time projection driven by handles: tool results whose handle is Collapsed render as previews (originals untouched), freeing budget for more recent turns.

Token budget: system_stable + system_knowledge tokens are subtracted first. Remaining budget is allocated to history turns newest-first. The newest protected context units are always included. Every other context unit is included or dropped atomically.