perf(daytona): bulk upload files in single HTTP call

FileSyncManager now accepts an optional bulk_upload_fn callback.
When provided, all changed files are uploaded in one call instead
of iterating one-by-one with individual HTTP POSTs.

DaytonaEnvironment wires this to sandbox.fs.upload_files() which
batches everything into a single multipart POST — ~580 files goes
from ~5 min to <2s on init.

Parent directories are pre-created in one mkdir -p call.

Fixes #7362 (item 1).

tools/environments/file_sync.py

@@ -21,6 +21,7 @@ _FORCE_SYNC_ENV = "HERMES_FORCE_FILE_SYNC"
 
 # Transport callbacks provided by each backend
 UploadFn = Callable[[str, str], None]  # (host_path, remote_path) -> raises on failure
+BulkUploadFn = Callable[[list[tuple[str, str]]], None]  # [(host_path, remote_path), ...] -> raises on failure
 DeleteFn = Callable[[list[str]], None]  # (remote_paths) -> raises on failure
 GetFilesFn = Callable[[], list[tuple[str, str]]]  # () -> [(host_path, remote_path), ...]
 
@@ -76,9 +77,11 @@ class FileSyncManager:
         upload_fn: UploadFn,
         delete_fn: DeleteFn,
         sync_interval: float = _SYNC_INTERVAL_SECONDS,
+        bulk_upload_fn: BulkUploadFn | None = None,
     ):
         self._get_files_fn = get_files_fn
         self._upload_fn = upload_fn
+        self._bulk_upload_fn = bulk_upload_fn
         self._delete_fn = delete_fn
         self._synced_files: dict[str, tuple[float, int]] = {}  # remote_path -> (mtime, size)
         self._last_sync_time: float = 0.0  # monotonic; 0 ensures first sync runs
@@ -129,9 +132,13 @@ class FileSyncManager:
             logger.debug("file_sync: deleting %d stale remote file(s)", len(to_delete))
 
         try:
-            for host_path, remote_path in to_upload:
-                self._upload_fn(host_path, remote_path)
-                logger.debug("file_sync: uploaded %s -> %s", host_path, remote_path)
+            if to_upload and self._bulk_upload_fn is not None:
+                self._bulk_upload_fn(to_upload)
+                logger.debug("file_sync: bulk-uploaded %d file(s)", len(to_upload))
+            else:
+                for host_path, remote_path in to_upload:
+                    self._upload_fn(host_path, remote_path)
+                    logger.debug("file_sync: uploaded %s -> %s", host_path, remote_path)
 
             if to_delete:
                 self._delete_fn(to_delete)