feat: split API and provider specs into separate llama-stack-api pkg

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

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.*
- Preserved git history using git mv for moved files
- Configured local editable install for development workflow
- Updated linting and type-checking configuration for both packages
- Rebased on top of upstream src/ layout changes

Testing

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

Next Steps

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

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

src/llama_stack/providers/inline/batches/reference/batches.py

@@ -13,13 +13,10 @@ import uuid
 from io import BytesIO
 from typing import Any, Literal
 
-from openai.types.batch import BatchError, Errors
-from pydantic import BaseModel
-
-from llama_stack.apis.batches import Batches, BatchObject, ListBatchesResponse
-from llama_stack.apis.common.errors import ConflictError, ResourceNotFoundError
-from llama_stack.apis.files import Files, OpenAIFilePurpose
-from llama_stack.apis.inference import (
+from llama_stack_api.apis.batches import Batches, BatchObject, ListBatchesResponse
+from llama_stack_api.apis.common.errors import ConflictError, ResourceNotFoundError
+from llama_stack_api.apis.files import Files, OpenAIFilePurpose
+from llama_stack_api.apis.inference import (
     Inference,
     OpenAIAssistantMessageParam,
     OpenAIChatCompletionRequestWithExtraBody,
@@ -31,7 +28,10 @@ from llama_stack.apis.inference import (
     OpenAIToolMessageParam,
     OpenAIUserMessageParam,
 )
-from llama_stack.apis.models import Models
+from llama_stack_api.apis.models import Models
+from openai.types.batch import BatchError, Errors
+from pydantic import BaseModel
+
 from llama_stack.log import get_logger
 from llama_stack.providers.utils.kvstore import KVStore