Adapt all environment env.py files to use shared task loader (HF + local)

[n0w0f]

Context

PR #328 standardized all task configs and introduced corral.utils.task_loader as a shared utility for loading tasks from HuggingFace or local JSON directories. Catalyst env.py was refactored as the reference implementation.

Task

Migrate the remaining environment env.py files to use the shared task loader instead of their custom load_tasks_from_json() functions:

• tasks/ml/src/ml/env.py
• tasks/resistor_network/src/resistor_network/env.py
• tasks/corral_md/src/corral_md/env.py
• tasks/afm/src/env.py
• tasks/spectra_elucidation/spectra_elucidation/env.py
• tasks/retrosynthesis/retrosynthesis/env.py

For each environment:

1. Replace custom load_tasks_from_json() with load_task_entries() / load_task_entries_from_env_package() from corral.utils.task_loader
2. Add an entries_to_task_definitions() function that maps entries to TaskDefinition using the env's scoring function registry (see catalyst env.py for reference)
3. Update create_environments() to accept local_dir (local) or environment (HF) kwargs
4. Remove duplicate TaskGroupEnvironment classes in ml, corral_md, and afm — use the shared one from corral.utils.task_group
5. Fix stale path references (retrosynthesis: tasks/subtasks → tasks_json/subtasks_json, corral_md: old category paths, afm: src/enviroment/)

Reference

• Shared loader: src/corral/utils/task_loader.py
• Reference env.py: tasks/catalyst/src/catalyst/env.py
• HF dataset: jablonkagroup/corral-environment-tasks