Improve structure and evaluation clarity of Gambit Digest entries

### Description

To enhance the readability, analytical value, and shareability of each digest entry, consider the following structural improvements for future issues of **Gambit Digest**:

#### Analytical Suggestions

* Include a brief **evaluation shift summary** for each line
*e.g.*: `"+1.3 → -2.1 after 8...hxg6?"`
This helps readers immediately gauge the volatility and tactical swing.

* Add a **“Best defended by...”** line
Suggest the engine-preferred move and resulting eval if Black/White plays accurately, useful for contrasting chaos with best play.

#### Analysis Summary Block

Create a small structured section under each line, such as:

```markdown
### Summary
- Motif: Center destabilization
- Volatility: 7.1 / 10
- Deviation Depth: Move 5
- Evaluation Swing: +0.6 → -3.2
- Best Defended By: 8... Be6
```

#### Visual Improvements (Optional)

* Embed **Lichess interactive boards** (e.g., [Lichess Studies](https://lichess.org/study) for each main line.
* Consider using a **PGN viewer embed** for inline move navigation (e.g. [pgn-viewer-js](https://github.com/mliebelt/PgnViewerJS) or GitHub-compatible markdown renderers).
* Optionally, use FEN thumbnails or clickable diagrams for key turning points.

_This issue tracks long-term formatting and presentation improvements to **Gambit Digest** publications. Feel free to update this thread with additional formatting proposals or implementation notes._

Look at existing Gambit Digest entries in the repository to understand the current format. The work involves updating the content generation or templating logic, likely in Python scripts that produce the markdown. Check for any existing scripts in the repository that handle digest creation. The goal is to modify the output to include the new structured sections like evaluation shift summaries and analysis blocks, and optionally integrate with Lichess or PGN viewers.

Written by the indexing model from the issue text.