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This section details on the original issue you should resolve

<issue_title>ENH: Improve Stability Margin</issue_title>
<issue_description>Currently we use the rocket's total center of pressure to compute the stability margin of the Flight class.

Since this center of pressure is defined based on the normal force coefficient derivative with respect to the angle of attack (cnalpha) we end up with a curve that does not change with the angle of attack, as reported by user Eli [ARIS]
(dvoeli05_67950) in our discord.

On RocketPy:

On OpenRocket:

As you can see, in OpenRocket the stability margin is much more "dynamic" than ours.

Describe the solution you'd like

In the Flight class, instead of using the angle of attack independent center of pressure for the stability margin calculations :

$$CP = \frac{ \sum (C_{N})_{\alpha} \cdot (X_{cp})_{\text{surface}}} {\sum (C_{N})_{\alpha}}$$

We should use a calculation that is dependent on alpha:

$$CP = \frac{ \sum C_{N}(\alpha) \cdot (X_{cp})_{\text{surface}}} {\sum C_{N}(\alpha) }$$

References:

• https://openrocket.info/documentation.html
• https://github.com/openrocket/openrocket</issue_description>

<agent_instructions>Please solve the issue described here.

Make a plan, find where in the code you're going to implement new changes. Then implement it following project guidelines.</agent_instructions>

Comments on the Issue (you are@copilot in this section)