ENH: Add simplified opening shock force estimation

[ArthurJWH]

Moving forward with PR #1050 : Add opening shock force estimation to Parachute class

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.55%. Comparing base (e0ff281) to head (0d32061).
⚠️ Report is 27 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1092      +/-   ##
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+ Coverage    82.18%   82.55%   +0.37%     
===========================================
  Files          122      128       +6     
  Lines        16355    16558     +203     
===========================================
+ Hits         13441    13670     +229     
+ Misses        2914     2888      -26     

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[Gui-FernandesBR]

Approved. Moving this out of Parachute into utilities is the right call, and the migration is complete: grep -n "shock" rocketpy/rocket/parachute.py comes back empty, so nothing was left behind from #1050.

What I checked locally:

• pytest tests/unit/test_utilities.py — 39 passed, 2 skipped
• ruff check clean, ruff format --check clean, pylint rocketpy/utilities.py — 10.00/10
• The formula matches Knacke's Cx * Cd*S * q. Spot-checking a realistic case (cd_s=10, rho=1.225, V=30 m/s, Cx=1.5) gives ~8.3 kN, which is the right order of magnitude for sizing a shock cord.
• The function is pure and nothing in the flight path calls it, so this is a pure addition with no regression surface.
• It picks up the API reference automatically, since docs/reference/classes/utils/utilities.rst uses .. automodule:: rocketpy.utilities :members:.

One nit, not blocking — in the opening_shock_coefficient docstring:

        :meth:`calculate_opening_shock_force`. Typical values range from

That target is left over from the Parachute-method version in #1050 and no longer exists anywhere in the repo (this line is its only occurrence). Two small consequences: it is a dangling cross-reference, and docs.yml builds with -W --keep-going — that workflow is scoped to PRs targeting master, so it won't go red here, but it could surface on the next develop -> master PR. It is also self-referential, since the parameter is described as feeding the very function it is documented in.

A one-liner fixes it, e.g.:

    opening_shock_coefficient : float, optional
        Empirical coefficient (commonly noted Cx) used to estimate the
        peak transient force experienced during parachute inflation.
        Typical values range from 1.2 to 2.0 depending on the deployment
        method and canopy type. Default value is 1.5.

Happy either way — feel free to fold it in here, or we can take it in a follow-up.

Two things I looked at that need no action: a negative velocity (descent, vz < 0) returns the same force as the positive case, which is correct given the V**2; and the function isn't re-exported in rocketpy/__init__.py, but no utilities function is (fin_flutter_analysis, calculate_equilibrium_altitude and friends aren't either), so it matches the existing convention.