Reintegrate drone_models and drone_controllers into crazyflow

[amacati]

drone-models

Previous state

Drone definitions and dynamics lived in a separate drone-models package, pulled in as a PyPI dependency / git submodule (submodules/drone-models, import drone_models). The MJCF files, meshes and parameters were resolved via drone_models.__file__, and the dynamics were imported into crazyflow/sim/physics.py.

Naming ambiguities

"Model" was overloaded three ways — the MuJoCo MJX model, the dynamics formulation, and the drone hardware. "models", "physics" and "dynamics" were often used interchangeably. These disambiguities have been fixed in the same step:

Concept	Before	After
Dynamics	Physics / models / dynamics	Dynamics / dynamics
Drone hardware	drone_model (param/attr)	drone
MuJoCo model	model (spec, file name)	mjx_model

Proposed naming scheme

• drone — a hardware platform (cf2x_L250, cf21B_500, …).
• dynamics — a physics formulation that advances the state (first_principles, so_rpy, so_rpy_rotor, so_rpy_rotor_drag), selected via the Dynamics enum.
• mjx_model — the MuJoCo MJX model used for kinematics/rendering.

We avoid the use of model where possible because it is ambiguous.

Package split

The vendored package is split by what the files are:

• crazyflow/drones/ — hardware descriptions: MJCF *.xml, meshes (assets/), and shared params.toml (mass, inertia, thrust/torque curves). available_drones enumerates platforms.
• crazyflow/dynamics/ — the dynamics themselves: one subpackage per fidelity level (each with dynamics.py + params.toml), plus core.py (Dynamics, parametrize), symbols.py, transform.py, and utils/. Written backend-agnostic (Array API: NumPy/JAX/PyTorch) and CasADi-symbolic, so the dynamics stay usable standalone for estimation/control.
  available_dynamics / dynamics_features enumerate and introspect them.

Other resulting changes

• Removed the drone-models dependency and submodule and added package-data globs for the vendored XML/STL/TOML.
• Deleted crazyflow/sim/physics.py; dynamics selection now lives in crazyflow/dynamics.
• Added crazyflow/_typing.py (Array/ArrayLike shim until array-api typing lands).
• Mechanical renames across docs, examples and tests (physics→dynamics, drone_model→drone);
  docs/user-guide/physics-models.md → dynamics-models.md.

Follow-up (separate PR)

• Move to_xp (crazyflow/dynamics/utils/__init__.py) to the general crazyflow/utils.py. It's a generic Array-API helper, not dynamics-specific.
• Reconsider home of the transform/rotation helpers (crazyflow/dynamics/transform.py, crazyflow/dynamics/utils/rotation.py). Several are general-purpose and may belong in shared utils.

drone-controllers

Previous state

Controllers lived in a separate drone-controllers package, pulled in as a PyPI dependency and git submodule (submodules/drone-controllers, import drone_controllers).

Package move

Vendored into crazyflow/control/, mirroring crazyflow/dynamics/: mellinger/ subpackage (controller functions + params.toml), core.py (parametrize, param loaders), control.py (Control enum), transform.py.

Unification

Previously the controller functions, the sim data structs, and the controller-to-SimData adapters were split across packages. They now live together in crazyflow/control/mellinger/control.py, the same way each dynamics module co-locates dynamics + Params + sim_dynamics.

API changes

• drone_model param renamed to drone (consistent with dynamics).
• load_params split into load_params(controller, drone) (raw, name-keyed loader) and load_fn_params(fn, drone) (per-function selection + signature filter).
• Integral errors are explicit named arguments (pos_err_i, r_int_error) instead of a generic ctrl_errors tuple.
• Sim adapters renamed control_<stage> and registered in the step pipeline under explicit role-based stage names (state_controller, attitude_controller, force_torque_controller, commit_attitude), so the pipeline is readable and the names are a stable insertion API.

Other resulting changes

• Removed the drone-controllers dependency and submodule.
• Added array-api-compat and array-api-extra as direct dependencies (were transitive via the package).
• Added tests (tests/unit/control/) and docs (docs/user-guide/control/).

[ratheron]

Thanks for working on this integration! This will make the entry to Crazyflow easier

[amacati]

Latest changes are all in and ready for another review

[ratheron]

Looks like you found a clean solution for the parameterize after all. I like it!
Left some minor comments

[ratheron]

Looks like you found a clean solution for the parameterize after all. I like it!
Left some minor comments

[ratheron]

The description of the models in the docs is wrong. Besides that, I can approve this PR now. Thanks for the work!