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/cli/stack/utils.py

@@ -1,151 +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.
-
-import json
-import sys
-from enum import Enum
-from functools import lru_cache
-from pathlib import Path
-
-import yaml
-from termcolor import cprint
-
-from llama_stack.core.datatypes import (
-    BuildConfig,
-    Provider,
-    StackRunConfig,
-    StorageConfig,
-)
-from llama_stack.core.distribution import get_provider_registry
-from llama_stack.core.resolver import InvalidProviderError
-from llama_stack.core.storage.datatypes import (
-    InferenceStoreReference,
-    KVStoreReference,
-    ServerStoresConfig,
-    SqliteKVStoreConfig,
-    SqliteSqlStoreConfig,
-    SqlStoreReference,
-)
-from llama_stack.core.utils.config_dirs import DISTRIBS_BASE_DIR, EXTERNAL_PROVIDERS_DIR
-from llama_stack.core.utils.dynamic import instantiate_class_type
-from llama_stack.core.utils.image_types import LlamaStackImageType
-from llama_stack.providers.datatypes import Api
-
-TEMPLATES_PATH = Path(__file__).parent.parent.parent / "distributions"
-
-
-class ImageType(Enum):
-    CONTAINER = "container"
-    VENV = "venv"
-
-
-def print_subcommand_description(parser, subparsers):
-    """Print descriptions of subcommands."""
-    description_text = ""
-    for name, subcommand in subparsers.choices.items():
-        description = subcommand.description
-        description_text += f"  {name:<21} {description}\n"
-    parser.epilog = description_text
-
-
-def generate_run_config(
-    build_config: BuildConfig,
-    build_dir: Path,
-    image_name: str,
-) -> Path:
-    """
-    Generate a run.yaml template file for user to edit from a build.yaml file
-    """
-    apis = list(build_config.distribution_spec.providers.keys())
-    distro_dir = DISTRIBS_BASE_DIR / image_name
-    run_config = StackRunConfig(
-        container_image=(image_name if build_config.image_type == LlamaStackImageType.CONTAINER.value else None),
-        image_name=image_name,
-        apis=apis,
-        providers={},
-        storage=StorageConfig(
-            backends={
-                "kv_default": SqliteKVStoreConfig(db_path=str(distro_dir / "kvstore.db")),
-                "sql_default": SqliteSqlStoreConfig(db_path=str(distro_dir / "sql_store.db")),
-            },
-            stores=ServerStoresConfig(
-                metadata=KVStoreReference(backend="kv_default", namespace="registry"),
-                inference=InferenceStoreReference(backend="sql_default", table_name="inference_store"),
-                conversations=SqlStoreReference(backend="sql_default", table_name="openai_conversations"),
-            ),
-        ),
-        external_providers_dir=build_config.external_providers_dir
-        if build_config.external_providers_dir
-        else EXTERNAL_PROVIDERS_DIR,
-    )
-    # build providers dict
-    provider_registry = get_provider_registry(build_config)
-    for api in apis:
-        run_config.providers[api] = []
-        providers = build_config.distribution_spec.providers[api]
-
-        for provider in providers:
-            pid = provider.provider_type.split("::")[-1]
-
-            p = provider_registry[Api(api)][provider.provider_type]
-            if p.deprecation_error:
-                raise InvalidProviderError(p.deprecation_error)
-
-            try:
-                config_type = instantiate_class_type(provider_registry[Api(api)][provider.provider_type].config_class)
-            except (ModuleNotFoundError, ValueError) as exc:
-                # HACK ALERT:
-                # This code executes after building is done, the import cannot work since the
-                # package is either available in the venv or container - not available on the host.
-                # TODO: use a "is_external" flag in ProviderSpec to check if the provider is
-                # external
-                cprint(
-                    f"Failed to import provider {provider.provider_type} for API {api} - assuming it's external, skipping: {exc}",
-                    color="yellow",
-                    file=sys.stderr,
-                )
-                # Set config_type to None to avoid UnboundLocalError
-                config_type = None
-
-            if config_type is not None and hasattr(config_type, "sample_run_config"):
-                config = config_type.sample_run_config(__distro_dir__=f"~/.llama/distributions/{image_name}")
-            else:
-                config = {}
-
-            p_spec = Provider(
-                provider_id=pid,
-                provider_type=provider.provider_type,
-                config=config,
-                module=provider.module,
-            )
-            run_config.providers[api].append(p_spec)
-
-    run_config_file = build_dir / f"{image_name}-run.yaml"
-
-    with open(run_config_file, "w") as f:
-        to_write = json.loads(run_config.model_dump_json())
-        f.write(yaml.dump(to_write, sort_keys=False))
-
-    # Only print this message for non-container builds since it will be displayed before the
-    # container is built
-    # For non-container builds, the run.yaml is generated at the very end of the build process so it
-    # makes sense to display this message
-    if build_config.image_type != LlamaStackImageType.CONTAINER.value:
-        cprint(f"You can now run your stack with `llama stack run {run_config_file}`", color="green", file=sys.stderr)
-    return run_config_file
-
-
-@lru_cache
-def available_templates_specs() -> dict[str, BuildConfig]:
-    import yaml
-
-    template_specs = {}
-    for p in TEMPLATES_PATH.rglob("*build.yaml"):
-        template_name = p.parent.name
-        with open(p) as f:
-            build_config = BuildConfig(**yaml.safe_load(f))
-            template_specs[template_name] = build_config
-    return template_specs