ENH: restore concrete generic Parachute class

[Gui-FernandesBR]

Summary

Addresses @MateusStano's pre-release review comments on #1048 (the HemisphericalParachute design concern, the noise parameter, and the drag_coefficient docstring), before the v1.13.0 tag is published.

The #958 refactor effectively renamed the concrete Parachute into HemisphericalParachute and left the old name as an abstract base — the hemispherical added-mass physics has been Parachute's behavior since at least v1.11 (the old hard-coded R = 1.5). That made Parachute(...) un-instantiable (a breaking change) without adding modeling capability, since there is only one concrete geometry.

Changes

• Parachute is concrete again, with its exact v1.12.1 signature and physics (u_dot, added mass, serialization move back into it). User code from v1.12.x runs unchanged, warning-free, with identical results. parachute_type is now a class attribute ("generic").
• HemisphericalParachute becomes a thin subclass: it makes the canopy geometry explicit, keeps the door open for future geometry-specific models (parafoil, flat circular, ...), and does not expose the noise parameter — noisy trigger readings should come from the Sensors infrastructure instead. Its drag_coefficient docs no longer suggest flat-circular/extended-skirt values (those stay on the generic class, where they make sense).
• Legacy Rocket.add_parachute(name, cd_s, ...) builds a generic Parachute again, keeping the FutureWarning nudge towards the object-passing API.
• Serialization: legacy .rpy signatures (rocketpy.rocket.parachute.Parachute) remap to the generic class at its new module path; round-trips preserve the concrete class.
• Docs: user guides and example notebooks return to the generic Parachute (several pass noise, which the subclass no longer accepts — including hedy_flight_sim.ipynb, which was never migrated and would break as released). The v1.13.0 changelog no longer lists a breaking change for parachutes.

Verification

• Full unit suite: 1690 passed, 13 skipped.
• Parachute-related flight integration tests: 4 passed.
• End-to-end smoke: generic Parachute with historical signature reproduces the v1.12 radius/added-mass values; legacy kwargs path emits exactly one FutureWarning and returns a Parachute; legacy .rpy decode reconstructs a generic Parachute with the noise field preserved.

Release note

This PR should be merged to develop and flow to master through #1060 before tagging v1.13.0, so the release ships without the parachute breaking change.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 96.77419% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.83%. Comparing base (f464601) to head (3e84998).

Files with missing lines	Patch %	Lines
rocketpy/rocket/parachutes/parachute.py	96.49%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1061      +/-   ##
===========================================
- Coverage    81.84%   81.83%   -0.02%     
===========================================
  Files          118      118              
  Lines        15254    15241      -13     
===========================================
- Hits         12485    12472      -13     
  Misses        2769     2769              

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