Missing tests for experiment_state, merge, merge_task

[SahilKumar75]

Context

Three new modules were added with no test coverage:

Module	Purpose
app/state/experiment_state.py	SQLite-backed experiment run persistence
trainer/merge.py	Merges a trained LoRA/QLoRA adapter into the base model
workers/merge_task.py	Celery task wrapping the merge operation

Tasks

app/state/experiment_state.py

• Test save_experiment_run() writes to and reads back from SQLite correctly
• Test ExperimentState.load_runs() returns correct ExperimentRun objects
• Test delete_run() removes from DB and from in-memory list
• Test toggle_run_selection() adds and removes IDs correctly
• Use a temporary DB path (via tmp_path fixture or EXPERIMENT_DB env var)

trainer/merge.py

• Test merge_adapter() is callable with mocked model / PEFT dependencies
• Test it raises with a clear error when the adapter path does not exist

workers/merge_task.py

• Mock Celery and test the task body logic (similar to tests/test_workers.py pattern)
• Test status updates are published correctly

Good first issue tips

See tests/test_workers.py and tests/test_api.py for the mocking patterns already in use. Run the suite with poetry run pytest.