[aiyagari] MAINT: transfer np.sum(a * b) to a @ b

[mmcky]

This PR fixes part of #463

• apply fix and compare to original code
• remove original code and comparison code

[github-actions]

🚀 Deployed on https://68537fcaed2d0e1c718588b3--nostalgic-wright-5fa355.netlify.app

[Copilot]

Pull Request Overview

This PR updates the Aiyagari lecture notebook by synchronizing Jupytext metadata, standardizing code-cell directives, and refactoring the capital‐supply calculation to use the @ operator instead of np.sum.

• Add format_version and jupytext_version to notebook metadata and adjust kernel display name.
• Change all {code-cell} directives to use ipython3 and the :tags: syntax.
• Introduce prices_to_capital_stock and replace np.sum(a * b) with asset_probs @ am.a_vals, retaining the original results for comparison.

Comments suppressed due to low confidence (2)

lectures/aiyagari.md:472

• [nitpick] The parameter name am is ambiguous; consider renaming it to something like household or hh to clarify that it’s an instance of the Household class.

def prices_to_capital_stock(am, r):

lectures/aiyagari.md:464

• [nitpick] Function name rd is not very descriptive; consider renaming it to something like interest_rate_from_capital or capital_demand_rate for clarity.

def rd(K):

[Copilot]

The variable am_ddp is assigned but never used; it can be removed to reduce clutter.

Suggested change

am_ddp = DiscreteDP(am.R, am.Q, am.β)

[mmcky]

@HumphreyYang this is an easy one, but would you mind reading through #463 (comment) and letting me know if you approve of this change to:

• verify change is correct
• check the assert between original code and new code

[HumphreyYang]

Hi @mmcky, this looks great to me.

I think we can go ahead with a global switch, as I don't expect this change to cause much trouble.

After that, we can review all the updated lectures to ensure they’re consistent with the previous results!