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/batches/batches.py

@@ -1,96 +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 Literal, Protocol, runtime_checkable
-
-from pydantic import BaseModel, Field
-
-from llama_stack.apis.version import LLAMA_STACK_API_V1
-from llama_stack.schema_utils import json_schema_type, webmethod
-
-try:
-    from openai.types import Batch as BatchObject
-except ImportError as e:
-    raise ImportError("OpenAI package is required for batches API. Please install it with: pip install openai") from e
-
-
-@json_schema_type
-class ListBatchesResponse(BaseModel):
-    """Response containing a list of batch objects."""
-
-    object: Literal["list"] = "list"
-    data: list[BatchObject] = Field(..., description="List of batch objects")
-    first_id: str | None = Field(default=None, description="ID of the first batch in the list")
-    last_id: str | None = Field(default=None, description="ID of the last batch in the list")
-    has_more: bool = Field(default=False, description="Whether there are more batches available")
-
-
-@runtime_checkable
-class Batches(Protocol):
-    """
-    The Batches API enables efficient processing of multiple requests in a single operation,
-    particularly useful for processing large datasets, batch evaluation workflows, and
-    cost-effective inference at scale.
-
-    The API is designed to allow use of openai client libraries for seamless integration.
-
-    This API provides the following extensions:
-     - idempotent batch creation
-
-    Note: This API is currently under active development and may undergo changes.
-    """
-
-    @webmethod(route="/batches", method="POST", level=LLAMA_STACK_API_V1)
-    async def create_batch(
-        self,
-        input_file_id: str,
-        endpoint: str,
-        completion_window: Literal["24h"],
-        metadata: dict[str, str] | None = None,
-        idempotency_key: str | None = None,
-    ) -> BatchObject:
-        """Create a new batch for processing multiple API requests.
-
-        :param input_file_id: The ID of an uploaded file containing requests for the batch.
-        :param endpoint: The endpoint to be used for all requests in the batch.
-        :param completion_window: The time window within which the batch should be processed.
-        :param metadata: Optional metadata for the batch.
-        :param idempotency_key: Optional idempotency key. When provided, enables idempotent behavior.
-        :returns: The created batch object.
-        """
-        ...
-
-    @webmethod(route="/batches/{batch_id}", method="GET", level=LLAMA_STACK_API_V1)
-    async def retrieve_batch(self, batch_id: str) -> BatchObject:
-        """Retrieve information about a specific batch.
-
-        :param batch_id: The ID of the batch to retrieve.
-        :returns: The batch object.
-        """
-        ...
-
-    @webmethod(route="/batches/{batch_id}/cancel", method="POST", level=LLAMA_STACK_API_V1)
-    async def cancel_batch(self, batch_id: str) -> BatchObject:
-        """Cancel a batch that is in progress.
-
-        :param batch_id: The ID of the batch to cancel.
-        :returns: The updated batch object.
-        """
-        ...
-
-    @webmethod(route="/batches", method="GET", level=LLAMA_STACK_API_V1)
-    async def list_batches(
-        self,
-        after: str | None = None,
-        limit: int = 20,
-    ) -> ListBatchesResponse:
-        """List all batches for the current user.
-
-        :param after: A cursor for pagination; returns batches after this batch ID.
-        :param limit: Number of batches to return (default 20, max 100).
-        :returns: A list of batch objects.
-        """
-        ...