Fix Fourier example images not building in documentation

[Copilot]

• Understand the issue: code-block directives in fourier.py don't execute code or generate images
• Change code-block:: python directives to plot:: directives for examples that generate plots (lines 73-94, 124-145)
• Add complete setup code to plot directives so they are self-contained and can execute properly
• Keep code-block for examples that are purely for syntax demonstration

Summary

Fixed rendering issues by including setup code in plot directives:

1. Lines 73-94: Plot the prior fourier seasonality trend (now includes full setup)
2. Lines 124-145: Plot with hierarchical coordinates (now includes full setup)

Each plot directive is now self-contained with all necessary imports and setup code, ensuring the yearly variable is properly defined when the plot executes. The setup code is still shown separately in code-block:: directives for educational reference, but the plot directives contain complete working examples.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Fourier example images not building</issue_title>
<issue_description>
Reference: https://www.pymc-marketing.io/en/stable/api/generated/pymc_marketing.mmm.fourier.html
</issue_description>

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

@OriolAbril The first block of code in the [source file](https://github.com/pymc-labs/pymc-marketing/blob/main/pymc_marketing/mmm/fourier.py) is using the matplotlib `plot` directive so the images are shown but the code isn't (this is the default behaviour but can be configured). The other code blocks are using the `code-block` directive which is only for syntax highlight and monospaced font, it won't execute the code inside it.

The code-block directive should be changed to either the plot directive or the ipython one.</comment_new>

• Fixes Fourier example images not building #1709

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

---

📚 Documentation preview 📚: https://pymc-marketing--2067.org.readthedocs.build/en/2067/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.56%. Comparing base (daba54b) to head (f89f24e).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2067   +/-   ##
=======================================
  Coverage   92.56%   92.56%           
=======================================
  Files          68       68           
  Lines        9420     9420           
=======================================
  Hits         8720     8720           
  Misses        700      700           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[juanitorduz]

Adress the feedback @copilot

[juanitorduz]

@copilot undo this change, we do not need this

[Copilot]

Reverted in commit 3ed3567. The setup code block is now back to code-block:: python.

[juanitorduz]

Remove this change as we do not need it @copilot

[Copilot]

Reverted in commit 3ed3567. The hierarchical setup code block is now back to code-block:: python.

[Copilot]

Adress the feedback @copilot

Addressed in commit 3ed3567. Reverted the setup code blocks (lines 55-69 and 95-107) back to code-block:: directives. Only the two examples that actually generate plots (lines 73-81 and 111-120) remain as plot:: directives.

[juanitorduz]

@copilot

[Copilot]

@copilot

Addressed the rendering issue in commit 582e9c2. Both plot directives now include the complete setup code so they execute properly and generate images.

[juanitorduz]

@williambdean WDYT?