Addition of IAG dynamic stall model as UAMod=9

[hkross]

This pull request is not ready to be merged.

All tests pass (comment line changes only); all development is finished; documentation has been updated

Feature or improvement description

• Addition of the IAG dynamic stall model (state space, first-order formulation) to UnsteadyAero as UAMod=9
• Implementation follows Bangaa et al. (https://www.mdpi.com/1996-1073/16/10/3994)

Related issue, if one exists
#2289

Impacted areas of the software

• AeroDyn
• UnsteadyAero

Generative AI usage
Generative AI was used in this work

• Theory document created manually
• AI used to create detailed implementation plan from theory document
• AI used to implement code changes
• AI used to conduct verification
• Assisted by: GitHub Copilot support@github.com
• Co-authored-by: Anthropic Claude claude@anthropic.com

Test results, if applicable
No impact on r-test results (changes to comment lines only)

• r-test branch merging required

To be completed before merging

• Verification against literature results
• Proofreading of documentation
• Addition of new r-test(s) using UAMod=9