[BUG] TrajectoryEvaluator silently drops user-supplied tools on serialization and exposes no public tools attribute #381

Checks

• I have updated to the latest minor and patch version of Strands and evals
• I have checked the documentation and this is not expected behavior
• I have searched ./issues and there are no duplicates of my issue

Strands Version

1.53.0

Strands Evals Version

main @ 9b245cf (1.2.1.dev)

Python Version

3.13.14

Operating System

Amazon Linux 2023 (aarch64)

Installation Method

git clone

Steps to Reproduce

from strands_evals.evaluators import TrajectoryEvaluator

te = TrajectoryEvaluator(rubric="r", tools=["my_pkg.calculator"])
print(te.to_dict())          # no 'tools' key at all
print(hasattr(te, "tools"))  # False

Expected Behavior

Consistent with OutputEvaluator after #379: serializable user tools survive to_dict()/Experiment.to_file(), non-serializable ones are skipped with a warning, and a public evaluator.tools attribute exists so tools can be re-attached after from_file().

Actual Behavior

• trajectory_evaluator.py:45-50 folds user tools into self._tools together with the three built-in scorer callables (exact_match_scorer, in_order_match_scorer, any_order_match_scorer), and the inherited Evaluator.to_dict() skips _-prefixed attrs — so user-supplied tools are silently dropped from serialization, with no warning, even fully serializable module-path strings.
• There is no public tools attribute (hasattr(te, "tools") is False), so the re-attach-after-loading recipe documented in fix: skip non-serializable tools in OutputEvaluator serialization #379 cannot be applied to this evaluator — which is the one feat(evaluators): allow custom tools on judge-based evaluators (Trajectory, Output, Multimodal) #324's own example used (TrajectoryEvaluator(tools=[verify_ticket_id])).

Verified on main @ 9b245cf.

Additional Context

Found during review of #379. After #379 merges, the two evaluators that both gained tools= in #324 have opposite contracts: OutputEvaluator has a public documented .tools property and persists the serializable subset with a warning; TrajectoryEvaluator has neither. Label suggestion: design / area-devx (I can't apply labels).

Possible Solution

Store user tools separately from the built-in scorers (e.g. self._user_tools), merge at evaluate() time, expose a tools property over the user subset, and mirror #379's to_dict() override. Needs a small design pass because _tools currently pre-mixes defaults with user tools.

Related Issues

#379, #324, #373