docs(l2): add guide to re generate blobs

[tomip01]

Motivation

We want to document how to create the blobs for the state reconstruct test.

[Copilot]

Pull Request Overview

This PR adds documentation for regenerating blob fixtures used in state reconstruction tests. The guide provides step-by-step instructions for modifying the L2 sequencer code to generate test blobs.

• Adds comprehensive documentation on regenerating blob test fixtures
• Integrates the new guide into the documentation table of contents under the L2 developers section

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
docs/developers/l2/state-reconstruction-blobs.md	New guide documenting the 3-step process for regenerating blob fixtures for state reconstruction tests
docs/SUMMARY.md	Adds entry for the new blob regeneration guide in the L2 section

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[JereSalo]

Maybe explain the reason about why we may need this. As you told me face to face this is because when we change something in the genesis its hash changes and as a consequence the blobs (that represent the blocks, that have pointers to parent block) become invalid.

Also, I'd like to know beforehand what the steps are going to be about, like a summary so the user doesn't follow the steps blindly without knowing what they're doing.