Add viam.spatialmath: FFI bindings for rust-utils orientation math

[Nick Hehr (HipsterBrown)]

Summary

Adds a new viam.spatialmath package: Pythonic, object-oriented wrappers over the shared rust-utils (libviam_rust_utils) spatial-math FFI, exposing orientation conversions whose results match Go rdk/spatialmath.

• Six wrapper classes — Quaternion, Vector3, OrientationVector, EulerAngles, AxisAngle, RotationMatrix — each owning an opaque FFI handle freed deterministically via weakref.finalize, with conversions between every representation.
• Proto bridges to viam.proto.common — OrientationVector/Vector3 from_proto/to_proto and Quaternion.from_pose/to_pose. Classes are radians-native; the proto bridges convert to/from the Viam protos' degrees convention at the boundary.
• Shared native loader — extracted the libviam_rust_utils ctypes loading from rpc/dial.py into viam/_native.py so both the dialer and spatialmath load one cached CDLL.
• No packaging change — the spatialmath symbols already ship in the bundled libviam_rust_utils, and hatchling already bundles the lib and picks up the new sub-package.

Conventions (matched to Go rdk/spatialmath)

• All angles are radians (Euler order Z-Y'-X" / yaw-pitch-roll); proto bridges convert deg↔rad.
• RotationMatrix.elements is row-major, matching rdk's convention.
• Zero-rotation AxisAngle returns the canonical axis (0, 0, 1), matching rdk.

Test Plan

• Golden parity — tests/spatialmath/fixtures/golden.json is generated from canonical Go rdk/spatialmath (generator in etc/spatialmath_golden/); a parametrized test asserts all conversions (orientation-vector, Euler, axis-angle, rotation-matrix) match within 1e-9 across identity / 90°-X / 180°-Y / tumble cases.
• Unit tests for each wrapper, proto bridges, and degrees/radians boundary behavior.
• Lifetime/leak — 10k-iteration churn + repeated component-read tests confirm no double-free/segfault; null-pointer input raises ValueError.
• ruff check and pyright clean on the new modules; dial.py refactor verified against existing dial tests.

🤖 Generated with Claude Code

[Nick Hehr (HipsterBrown)]

Ethan (@stuqdog) I've removed that Go module responsible for generating the golden.json test fixture and added a note to the JSON to mention how it was created. I can work on a follow up in the rust-utils library to upstream the parity test, so other consumers of the spatialmath utils benefit from those changes.

[Ethan (stuqdog)]

Didn't personally test everything but given that tests are passing, assuming golden.json came from RDK this all seems good to me!