Reimplement ergoExo/ADEPTModule as a compatibility façade and publish a deprecation path

[joglekara]

Motivation

Tests and downstream repositories depend on ergoExo.setup(), call(), val_and_grad(), custom module injection, mutable module attributes, existing return shapes, nested/resumed MLflow behavior, and artifact snapshots. The replacement architecture requires a staged migration rather than a flag day.

Scope

Implement legacy adapters over the new builder, prepared simulation, execution, analyzer, and tracker layers. Preserve supported behavior while directing new code to the replacement APIs.

Document unsupported mutation patterns and provide explicit replacements, such as creating an updated prepared simulation/state rather than mutating closure-captured fields.

Acceptance criteria

• ergoExo().setup(cfg) and exo(modules, args) preserve documented return shapes.
• val_and_grad() remains compatible or has a tested transitional adapter.
• Caller configs remain reusable and unmutated.
• Nested/resumed MLflow behavior is reproduced through the host-side tracker.
• Raw, units, derived-config, array-config, and artifact regression tests pass.
• Numerical integration tests cover legacy and new entry points.
• Existing custom solver injection has a tested adapter or actionable migration error.
• Direct state replacement needed by current tests has a supported transitional path.
• CLI forward/resume paths use the façade and are tested.
• Deprecation warnings, migration examples, version timeline, and removal policy are published.
• New internal implementations do not subclass ADEPTModule except for the façade.

Dependencies

• Builder/PreparedSimulation: Add logging-free SimulationSpec, SolverBuilder, PreparedSimulation, and solver registry #353.
• Pure JAX program and explicit data/objectives: Define an explicit pure-JAX JaxProgram boundary for continuous and discrete systems #350 and Make Params, State, Inputs, RNG, and objectives explicit #352.
• Tracker/ArtifactSink: Move MLflow behind host-side Tracker and ArtifactSink adapters #351.

Out of scope

• Removing legacy classes in this issue.
• Changing established output dictionaries or artifact formats.
• Silently emulating arbitrary Python mutation inside transformed execution.
• Requiring downstream migration before replacement APIs are available.