fix partial download progress showing 0% on restart

On restart, _emit_existing_download_progress() checked
downloaded_bytes_this_session to decide if a download was pending.
Since this field is always 0 in a new session, partially downloaded
models were reported as DownloadPending (0%) instead of DownloadOngoing
with their actual progress. Check downloaded_bytes (actual data on
disk) instead.

Closes #1042

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/exo/download/coordinator.py

@@ -324,7 +324,7 @@ class DownloadCoordinator:
                                 shard_metadata=progress.shard,
                                 total_bytes=progress.total_bytes,
                             )
-                        elif progress.downloaded_bytes_this_session.in_bytes == 0:
+                        elif progress.downloaded_bytes.in_bytes == 0:
                             status = DownloadPending(
                                 node_id=self.node_id,
                                 shard_metadata=progress.shard,

src/exo/master/api.py

@@ -149,12 +149,7 @@ from exo.shared.types.openai_responses import (
     ResponsesResponse,
 )
 from exo.shared.types.state import State
-from exo.shared.types.worker.instances import (
-    Instance,
-    InstanceId,
-    InstanceMeta,
-    MlxJacclInstance,
-)
+from exo.shared.types.worker.instances import Instance, InstanceId, InstanceMeta
 from exo.shared.types.worker.shards import Sharding
 from exo.utils.banner import print_startup_banner
 from exo.utils.channels import Receiver, Sender, channel
@@ -496,14 +491,6 @@ class API:
             shard_assignments = instance.shard_assignments
             placement_node_ids = list(shard_assignments.node_to_runner.keys())
 
-            # Derive instance_meta from the actual instance type, since
-            # place_instance() may override it (e.g., single-node → MlxRing)
-            actual_instance_meta = (
-                InstanceMeta.MlxJaccl
-                if isinstance(instance, MlxJacclInstance)
-                else InstanceMeta.MlxRing
-            )
-
             memory_delta_by_node: dict[str, int] = {}
             if placement_node_ids:
                 total_bytes = model_card.storage_size.in_bytes
@@ -516,14 +503,14 @@ class API:
             if (
                 model_card.model_id,
                 sharding,
-                actual_instance_meta,
+                instance_meta,
                 len(placement_node_ids),
             ) not in seen:
                 previews.append(
                     PlacementPreview(
                         model_id=model_card.model_id,
                         sharding=sharding,
-                        instance_meta=actual_instance_meta,
+                        instance_meta=instance_meta,
                         instance=instance,
                         memory_delta_by_node=memory_delta_by_node or None,
                         error=None,
@@ -533,7 +520,7 @@ class API:
                 (
                     model_card.model_id,
                     sharding,
-                    actual_instance_meta,
+                    instance_meta,
                     len(placement_node_ids),
                 )
             )