Function compact_session_loops 

pub fn compact_session_loops(
    session: &mut Session,
    current_loop_id: &str,
    strategy: &dyn BlockCompactionStrategy,
    config: &CompactionConfig,
    max_context_tokens: usize,
    counter: Option<&Arc<dyn TokenCounter>>,
)

Create CompactionBlocks for the current loop and earlier loops within scope. Mutates the session in place.

When counter is None, uses HeuristicTokenCounter (chars/4) as the default. The caller is responsible for persisting the session to disk afterward.