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 .`

src/llama_stack/apis/eval/eval.py

@@ -0,0 +1,169 @@
+# 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 Annotated, Any, Literal, Protocol
+
+from pydantic import BaseModel, Field
+
+from llama_stack.apis.agents import AgentConfig
+from llama_stack.apis.common.job_types import Job
+from llama_stack.apis.inference import SamplingParams, SystemMessage
+from llama_stack.apis.scoring import ScoringResult
+from llama_stack.apis.scoring_functions import ScoringFnParams
+from llama_stack.apis.version import LLAMA_STACK_API_V1, LLAMA_STACK_API_V1ALPHA
+from llama_stack.schema_utils import json_schema_type, register_schema, webmethod
+
+
+@json_schema_type
+class ModelCandidate(BaseModel):
+    """A model candidate for evaluation.
+
+    :param model: The model ID to evaluate.
+    :param sampling_params: The sampling parameters for the model.
+    :param system_message: (Optional) The system message providing instructions or context to the model.
+    """
+
+    type: Literal["model"] = "model"
+    model: str
+    sampling_params: SamplingParams
+    system_message: SystemMessage | None = None
+
+
+@json_schema_type
+class AgentCandidate(BaseModel):
+    """An agent candidate for evaluation.
+
+    :param config: The configuration for the agent candidate.
+    """
+
+    type: Literal["agent"] = "agent"
+    config: AgentConfig
+
+
+EvalCandidate = Annotated[ModelCandidate | AgentCandidate, Field(discriminator="type")]
+register_schema(EvalCandidate, name="EvalCandidate")
+
+
+@json_schema_type
+class BenchmarkConfig(BaseModel):
+    """A benchmark configuration for evaluation.
+
+    :param eval_candidate: The candidate to evaluate.
+    :param scoring_params: Map between scoring function id and parameters for each scoring function you want to run
+    :param num_examples: (Optional) The number of examples to evaluate. If not provided, all examples in the dataset will be evaluated
+    """
+
+    eval_candidate: EvalCandidate
+    scoring_params: dict[str, ScoringFnParams] = Field(
+        description="Map between scoring function id and parameters for each scoring function you want to run",
+        default_factory=dict,
+    )
+    num_examples: int | None = Field(
+        description="Number of examples to evaluate (useful for testing), if not provided, all examples in the dataset will be evaluated",
+        default=None,
+    )
+    # we could optinally add any specific dataset config here
+
+
+@json_schema_type
+class EvaluateResponse(BaseModel):
+    """The response from an evaluation.
+
+    :param generations: The generations from the evaluation.
+    :param scores: The scores from the evaluation.
+    """
+
+    generations: list[dict[str, Any]]
+    # each key in the dict is a scoring function name
+    scores: dict[str, ScoringResult]
+
+
+class Eval(Protocol):
+    """Evaluations
+
+    Llama Stack Evaluation API for running evaluations on model and agent candidates."""
+
+    @webmethod(route="/eval/benchmarks/{benchmark_id}/jobs", method="POST", level=LLAMA_STACK_API_V1, deprecated=True)
+    @webmethod(route="/eval/benchmarks/{benchmark_id}/jobs", method="POST", level=LLAMA_STACK_API_V1ALPHA)
+    async def run_eval(
+        self,
+        benchmark_id: str,
+        benchmark_config: BenchmarkConfig,
+    ) -> Job:
+        """Run an evaluation on a benchmark.
+
+        :param benchmark_id: The ID of the benchmark to run the evaluation on.
+        :param benchmark_config: The configuration for the benchmark.
+        :returns: The job that was created to run the evaluation.
+        """
+        ...
+
+    @webmethod(
+        route="/eval/benchmarks/{benchmark_id}/evaluations", method="POST", level=LLAMA_STACK_API_V1, deprecated=True
+    )
+    @webmethod(route="/eval/benchmarks/{benchmark_id}/evaluations", method="POST", level=LLAMA_STACK_API_V1ALPHA)
+    async def evaluate_rows(
+        self,
+        benchmark_id: str,
+        input_rows: list[dict[str, Any]],
+        scoring_functions: list[str],
+        benchmark_config: BenchmarkConfig,
+    ) -> EvaluateResponse:
+        """Evaluate a list of rows on a benchmark.
+
+        :param benchmark_id: The ID of the benchmark to run the evaluation on.
+        :param input_rows: The rows to evaluate.
+        :param scoring_functions: The scoring functions to use for the evaluation.
+        :param benchmark_config: The configuration for the benchmark.
+        :returns: EvaluateResponse object containing generations and scores.
+        """
+        ...
+
+    @webmethod(
+        route="/eval/benchmarks/{benchmark_id}/jobs/{job_id}", method="GET", level=LLAMA_STACK_API_V1, deprecated=True
+    )
+    @webmethod(route="/eval/benchmarks/{benchmark_id}/jobs/{job_id}", method="GET", level=LLAMA_STACK_API_V1ALPHA)
+    async def job_status(self, benchmark_id: str, job_id: str) -> Job:
+        """Get the status of a job.
+
+        :param benchmark_id: The ID of the benchmark to run the evaluation on.
+        :param job_id: The ID of the job to get the status of.
+        :returns: The status of the evaluation job.
+        """
+        ...
+
+    @webmethod(
+        route="/eval/benchmarks/{benchmark_id}/jobs/{job_id}",
+        method="DELETE",
+        level=LLAMA_STACK_API_V1,
+        deprecated=True,
+    )
+    @webmethod(route="/eval/benchmarks/{benchmark_id}/jobs/{job_id}", method="DELETE", level=LLAMA_STACK_API_V1ALPHA)
+    async def job_cancel(self, benchmark_id: str, job_id: str) -> None:
+        """Cancel a job.
+
+        :param benchmark_id: The ID of the benchmark to run the evaluation on.
+        :param job_id: The ID of the job to cancel.
+        """
+        ...
+
+    @webmethod(
+        route="/eval/benchmarks/{benchmark_id}/jobs/{job_id}/result",
+        method="GET",
+        level=LLAMA_STACK_API_V1,
+        deprecated=True,
+    )
+    @webmethod(
+        route="/eval/benchmarks/{benchmark_id}/jobs/{job_id}/result", method="GET", level=LLAMA_STACK_API_V1ALPHA
+    )
+    async def job_result(self, benchmark_id: str, job_id: str) -> EvaluateResponse:
+        """Get the result of a job.
+
+        :param benchmark_id: The ID of the benchmark to run the evaluation on.
+        :param job_id: The ID of the job to get the result of.
+        :returns: The result of the job.
+        """
+        ...