chore(package): migrate to src/ layout

Moved package code from llama_stack/ to src/llama_stack/ following Python
packaging best practices. Updated pyproject.toml, MANIFEST.in, and tool
configurations accordingly.

Public API and import paths remain unchanged. Developers will need to
reinstall in editable mode after pulling this change.

Also updated paths in pre-commit config, scripts, and GitHub workflows.

src/llama_stack/apis/datasetio/datasetio.py

@@ -0,0 +1,59 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+from typing import Any, Protocol, runtime_checkable
+
+from llama_stack.apis.common.responses import PaginatedResponse
+from llama_stack.apis.datasets import Dataset
+from llama_stack.apis.version import LLAMA_STACK_API_V1, LLAMA_STACK_API_V1BETA
+from llama_stack.schema_utils import webmethod
+
+
+class DatasetStore(Protocol):
+    def get_dataset(self, dataset_id: str) -> Dataset: ...
+
+
+@runtime_checkable
+class DatasetIO(Protocol):
+    # keeping for aligning with inference/safety, but this is not used
+    dataset_store: DatasetStore
+
+    @webmethod(route="/datasetio/iterrows/{dataset_id:path}", method="GET", deprecated=True, level=LLAMA_STACK_API_V1)
+    @webmethod(route="/datasetio/iterrows/{dataset_id:path}", method="GET", level=LLAMA_STACK_API_V1BETA)
+    async def iterrows(
+        self,
+        dataset_id: str,
+        start_index: int | None = None,
+        limit: int | None = None,
+    ) -> PaginatedResponse:
+        """Get a paginated list of rows from a dataset.
+
+        Uses offset-based pagination where:
+        - start_index: The starting index (0-based). If None, starts from beginning.
+        - limit: Number of items to return. If None or -1, returns all items.
+
+        The response includes:
+        - data: List of items for the current page.
+        - has_more: Whether there are more items available after this set.
+
+        :param dataset_id: The ID of the dataset to get the rows from.
+        :param start_index: Index into dataset for the first row to get. Get all rows if None.
+        :param limit: The number of rows to get.
+        :returns: A PaginatedResponse.
+        """
+        ...
+
+    @webmethod(
+        route="/datasetio/append-rows/{dataset_id:path}", method="POST", deprecated=True, level=LLAMA_STACK_API_V1
+    )
+    @webmethod(route="/datasetio/append-rows/{dataset_id:path}", method="POST", level=LLAMA_STACK_API_V1BETA)
+    async def append_rows(self, dataset_id: str, rows: list[dict[str, Any]]) -> None:
+        """Append rows to a dataset.
+
+        :param dataset_id: The ID of the dataset to append the rows to.
+        :param rows: The rows to append to the dataset.
+        """
+        ...