chore(package): migrate to src/ layout (#3920)

Migrates package structure to src/ layout following Python packaging
best practices.

All code moved from `llama_stack/` to `src/llama_stack/`. Public API
unchanged - imports remain `import llama_stack.*`.

Updated build configs, pre-commit hooks, scripts, and GitHub workflows
accordingly. All hooks pass, package builds cleanly.

**Developer note**: Reinstall after pulling: `pip install -e .`

llama_stack/providers/remote/datasetio/nvidia/datasetio.py

@@ -1,116 +0,0 @@
-# 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
-
-import aiohttp
-
-from llama_stack.apis.common.content_types import URL
-from llama_stack.apis.common.responses import PaginatedResponse
-from llama_stack.apis.common.type_system import ParamType
-from llama_stack.apis.datasets import Dataset
-
-from .config import NvidiaDatasetIOConfig
-
-
-class NvidiaDatasetIOAdapter:
-    """Nvidia NeMo DatasetIO API."""
-
-    def __init__(self, config: NvidiaDatasetIOConfig):
-        self.config = config
-        self.headers = {}
-
-    async def _make_request(
-        self,
-        method: str,
-        path: str,
-        headers: dict[str, Any] | None = None,
-        params: dict[str, Any] | None = None,
-        json: dict[str, Any] | None = None,
-        **kwargs,
-    ) -> dict[str, Any]:
-        """Helper method to make HTTP requests to the Customizer API."""
-        url = f"{self.config.datasets_url}{path}"
-        request_headers = self.headers.copy()
-
-        # Set default Content-Type for JSON requests
-        if json is not None:
-            request_headers["Content-Type"] = "application/json"
-
-        if headers:
-            request_headers.update(headers)
-
-        async with aiohttp.ClientSession(headers=request_headers) as session:
-            async with session.request(method, url, params=params, json=json, **kwargs) as response:
-                if response.status != 200:
-                    error_data = await response.json()
-                    raise Exception(f"API request failed: {error_data}")
-                return await response.json()
-
-    async def register_dataset(
-        self,
-        dataset_def: Dataset,
-    ) -> Dataset:
-        """Register a new dataset.
-
-        Args:
-            dataset_def [Dataset]: The dataset definition.
-                dataset_id [str]: The ID of the dataset.
-                source [DataSource]: The source of the dataset.
-                metadata [Dict[str, Any]]: The metadata of the dataset.
-                    format [str]: The format of the dataset.
-                    description [str]: The description of the dataset.
-        Returns:
-            Dataset
-        """
-        # add warnings for unsupported params
-        request_body = {
-            "name": dataset_def.identifier,
-            "namespace": self.config.dataset_namespace,
-            "files_url": dataset_def.source.uri,
-            "project": self.config.project_id,
-        }
-        if dataset_def.metadata:
-            request_body["format"] = dataset_def.metadata.get("format")
-            request_body["description"] = dataset_def.metadata.get("description")
-        await self._make_request(
-            "POST",
-            "/v1/datasets",
-            json=request_body,
-        )
-        return dataset_def
-
-    async def update_dataset(
-        self,
-        dataset_id: str,
-        dataset_schema: dict[str, ParamType],
-        url: URL,
-        provider_dataset_id: str | None = None,
-        provider_id: str | None = None,
-        metadata: dict[str, Any] | None = None,
-    ) -> None:
-        raise NotImplementedError("Not implemented")
-
-    async def unregister_dataset(
-        self,
-        dataset_id: str,
-    ) -> None:
-        await self._make_request(
-            "DELETE",
-            f"/v1/datasets/{self.config.dataset_namespace}/{dataset_id}",
-            headers={"Accept": "application/json", "Content-Type": "application/json"},
-        )
-
-    async def iterrows(
-        self,
-        dataset_id: str,
-        start_index: int | None = None,
-        limit: int | None = None,
-    ) -> PaginatedResponse:
-        raise NotImplementedError("Not implemented")
-
-    async def append_rows(self, dataset_id: str, rows: list[dict[str, Any]]) -> None:
-        raise NotImplementedError("Not implemented")