v0.9.0

A feature release adding state estimation, feedback control, wheeled kinematics, and
waypoint paths, plus a prelude and one-call entry points for the calculus core.

Added

• Const-evaluable solver constructors, AutoDiff new(), and Gaussian quadrature node
  tables / nodes. @rtmongold (#168)
• Add Vector/Matrix get / get_mut, Matrix::try_row / try_column, and
  Matrix::as_mut_slice_rows. @rtmongold (#185)
• Kinematics. A kinematics module with DifferentialDrive, a unicycle model, and
  dead-reckoning odometry, plus a kinematics demo. @kmolan (#170)
• State estimation. An estimation module with KalmanFilter and
  ExtendedKalmanFilter (the latter differentiating its nonlinear models for the
  Jacobians each step), a CovarianceUpdate choice for how the covariance is recomputed,
  cross-validation fixtures, and an estimation demo. @kmolan (#175)
• Particle filter. A bootstrap/SIR ParticleFilter with pluggable resampling and
  measurement likelihood, behind the alloc feature. @kmolan (#188)
• Control. A control module with Pid, a one-pole derivative filter
  (OnePoleLowPass), and the pure-pursuit path-following law. @kmolan (#179)
• Follow-the-gap. A reactive obstacle-avoidance controller in control, with an
  avoidance demo. @kmolan (#188)
• Waypoint paths. A motion module with PolylinePath and its arc-length,
  closest-point, and lookahead queries. @kmolan (#179)
• Random numbers. A random module with the RandomSource trait and the seedable
  Pcg32 generator, giving uniform and normal draws without a heap or std. @kmolan (#188)
• Prelude and one-call functions. multicalc::prelude for the traits and short
  functions worth importing together, plus derivative, second_derivative, partial,
  and integral, which need no configured backend. @kmolan (#198)
• General N×N determinant and inverse. Sizes past 4×4 now factor through LU instead of
  being unsupported; small sizes keep their closed forms. @kirloo (#184)
• 3D surface flux integral. flux_integral_3d and flux_integral_3d_custom.
  @mubasharameen485-cloud (#172)
• Property tests that LU and QR factorizations reconstruct their input matrix.
  @yvoolab (#189)
• A localization and obstacle-avoidance lap demo, with simulated lidar, an occupancy grid,
  a particle-filter localizer, latency benchmarks, and embedded smoke fixtures.
  @kmolan (#192)
• docs.rs now builds with all features so gated items appear in the published docs.
  @kmolan (#197)

Fixed

• Iterative integrators return IntegrateError::LimitsIllDefined instead of NaN
  if classify fails after validation. @rtmongold (#171)
• RK45 now handles zero-dimensional states without producing NaN norms.
  @terminalchai (#174)
• 2×2/3×3/4×4 Matrix::inverse reject near-singular inputs via an
  EPSILON-scaled det check instead of exact det == 0. @rtmongold (#181)
• Spatial small-angle Taylor cutoffs use 30 · EPSILON and (30 · EPSILON)²
  instead of fixed 1e-6 / 1e-12. @rtmongold (#190)
• The iterative and Gaussian integrators check their samples and return
  IntegrateError::NonFinite, instead of letting a blown-up integrand propagate into a
  garbage result. @SAY-5 (#180)
• The multi-variable integrators bounds-check the variable index and return the new
  IntegrateError::IndexOutOfRange. @Devil1716 (#178)

Changed

• Keep panicking Index / IndexMut as the ergonomic Matrix/Vector access path.
  Remove panicking row / column (use try_row / try_column). @rtmongold (#185)
• Vector-field functions renamed and re-exported. curl::get_2d,
  line_integral::get_2d, and the rest are now curl_2d, line_integral_2d, and so on,
  imported straight from vector_field. @kmolan (#199)
• Kalman filter takes a KalmanModel. The four model matrices are one named struct
  instead of four positional constructor arguments. @kmolan (#198)
• The crate root re-exports the differentiation, integration, and approximation types, so
  they can be named without their module paths. @kmolan (#198)
• Rewrote the test suite for readability: table-driven cases, named expectations, and
  shared helpers. @kmolan (#200)
• Golden fixture regeneration runs from a script in a local virtualenv with locked,
  hash-checked dependencies and a pinned timestamp, so a rerun produces the same bytes.
  @kmolan (#201)
• Dropped CI caching, which was causing flaky pipeline failures. @kmolan (#173)