Peritheos 0.4.0

Added

• Branch-aware coverage enforcement, Ruff lint and formatting gates, and a
  minimum-supported-dependency CI job.
• Literature-tagged numerical cases for all public EOS families and an
  independently solvable weighted least-squares fitting benchmark.
• Automatic GitHub Releases with source and wheel artifacts.
• Citation metadata, API stability, contribution, security, support, conduct,
  issue, and pull-request policies.
• Versioned Read the Docs builds using the locked uv documentation environment.
• Joint reference-isotherm and thermal parameter fitting with complete
  cross-covariance through fit_joint_eos.
• Per-observation correlated P-V and P-V-T covariance matrices and robust
  least-squares losses for all fitting entry points.
• Human-readable fit summaries and versioned, JSON-safe result export including
  model parameters, covariance, adjusted observations, diagnostics, and solver
  metadata.

Changed

• Uncertainty propagation tests now cover Monte Carlo state sampling, invalid
  covariance and option handling, one-sided numerical derivatives, wrapper
  behavior, and failed sampling; branch-aware project coverage exceeds 90%.
• Corrected the fourth-order Birch-Murnaghan documentation to match its
  implemented Eulerian-strain signs and exponents.
• Package maturity metadata now identifies the 0.4 development line as beta.
• The minimum supported NumPy version is now 1.21, matching the public typing
  APIs used by Peritheos.
• Distribution package discovery is restricted to peritheos, preventing
  generated documentation directories from entering or blocking builds.