Feature/duett

[michalbbednarczyk]

PR Description includes:
○Contributor name and NetID/email (1.5 pts):
michalb3 michalb3@illinois.edu

○Type of contribution (dataset+task/model/task) (1 pt):
dataset+task+model

○Link to original paper (required for reproducibility contributions) (1 pt):
https://arxiv.org/abs/2304.13017

○High-level description of implementation (1.5 pts):
This PR introduces a PyHealth-compliant full-pipeline integration of DuETT, representing a partial replication of the original paper.

○File guide listing which files to review (1 pt):

• pyhealth/datasets/physionet2012.py: Core dataset loader and parser.
• pyhealth/datasets/configs/physionet2012.yaml: Dataset schema configuration.
• pyhealth/tasks/physionet_mortality.py: Task definition and time-binning logic.
• pyhealth/processors/duett_processor.py: Custom feature processor for Z-score normalization and observation counts.
• pyhealth/models/duett.py: Core DuETT model and dual-attention architecture.
• pyhealth/datasets/__init__.py, pyhealth/tasks/__init__.py, pyhealth/processors/__init__.py, pyhealth/models/__init__.py
• examples/physionet2012_mortality_duett.py: Ablation study and usage example.
• runner.sh: Local execution script for the pipeline.
• tests/core/test_physionet2012.py: Dataset parsing tests.
• tests/core/test_physionet_mortality.py: Task extraction and binning tests.
• tests/core/test_duett_processor.py: Processor normalization tests.
• tests/core/test_duett.py: Model forward-pass and instantiation tests.
• docs/api/datasets/pyhealth.datasets.PhysioNet2012Dataset.rst
• docs/api/tasks/pyhealth.tasks.PhysioNetMortalityTask.rst
• docs/api/processors/pyhealth.processors.DuETTTimeSeriesProcessor.rst
• docs/api/models/pyhealth.models.DuETT.rst
• docs/api/datasets.rst, docs/api/tasks.rst, docs/api/models.rst: Index updates to render the new documentation pages.
  ○Follows example PR format from contribution guide (1 pt)