feat: split API and provider specs into separate llama-stack-api pkg (#3895)

# What does this PR do?

Extract API definitions and provider specifications into a standalone
llama-stack-api package that can be published to PyPI independently of
the main llama-stack server.


see: https://github.com/llamastack/llama-stack/pull/2978 and
https://github.com/llamastack/llama-stack/pull/2978#issuecomment-3145115942

Motivation

External providers currently import from llama-stack, which overrides
the installed version and causes dependency conflicts. This separation
allows external providers to:

- Install only the type definitions they need without server
dependencies
- Avoid version conflicts with the installed llama-stack package
- Be versioned and released independently

This enables us to re-enable external provider module tests that were
previously blocked by these import conflicts.

Changes

- Created llama-stack-api package with minimal dependencies (pydantic,
jsonschema)
- Moved APIs, providers datatypes, strong_typing, and schema_utils
- Updated all imports from llama_stack.* to llama_stack_api.*
- Configured local editable install for development workflow
- Updated linting and type-checking configuration for both packages

Next Steps

- Publish llama-stack-api to PyPI
- Update external provider dependencies
- Re-enable external provider module tests


Pre-cursor PRs to this one:

- #4093 
- #3954 
- #4064 

These PRs moved key pieces _out_ of the Api pkg, limiting the scope of
change here.


relates to #3237 

## Test Plan

Package builds successfully and can be imported independently. All
pre-commit hooks pass with expected exclusions maintained.

---------

Signed-off-by: Charlie Doern <cdoern@redhat.com>

src/llama_stack/apis/datasetio/datasetio.py

@@ -1,55 +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, 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_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", 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", 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.
-        """
-        ...