Preserve image-aware sparse QSA for Qwen vision

src/engine/metal/qwen_mtplx/session_checkpoint.rs

@@ -78,6 +78,9 @@ impl LiveSession {
             .as_ref()
             .ok_or("Qwen has no committed checkpoint")?;
         validate_tokens(&saved.token_ids, identity)?;
+        if !crate::engine::qwen_vision::compatible(&self.current_images) {
+            return Err("Qwen vision cache policy differs; rebuild the cache".into());
+        }
         if saved.mtp.is_some() != identity.mtp {
             return Err("Qwen checkpoint MTP configuration differs".into());
         }
@@ -179,6 +182,9 @@ impl LiveSession {
             );
         }
         validate_tokens(&manifest.tokens, identity)?;
+        if !crate::engine::qwen_vision::compatible(&manifest.images) {
+            return Err("Qwen vision cache policy differs; rebuild the cache".into());
+        }
         if !manifest.payload["mtp_history_snapshot"].is_null() != identity.mtp {
             return Err("Qwen checkpoint MTP payload differs".into());
         }