docs: add content to how-to landing pages

[asanvaq]

The following landing pages in the how-to section do not fit the required model:

• Crafting
• Chiseling
• Documentation

This PR updates them to fit the model. Metadata descriptions have also been added to those missing them.

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• I've followed the contribution guidelines.
• I've signed the CLA.
• I've successfully run make lint && make test.
• I've added or updated any relevant documentation.
• In documents I changed, I added a meta description if one was missing.
• I've updated the relevant release notes.

[Copilot]

Pull request overview

Updates Rockcraft’s “How-to” landing pages to better match the project’s landing-page model by adding missing meta descriptions and providing short, curated entry points into each how-to area.

Changes:

• Added/updated .. meta:: :description: blocks for how-to landing pages that were missing or overly generic.
• Expanded the Crafting and Chiseling landing pages with short overviews and curated :ref: link lists, while hiding the underlying toctrees.
• Added a brief introductory sentence to the Documentation landing page and normalized its toctree entries.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
docs/how-to/index.rst	Adds a meta description for the how-to landing page.
docs/how-to/documentation/index.rst	Adds a short intro line and normalizes the toctree entry format.
docs/how-to/crafting/index.rst	Reworks the landing page into a modeled overview with curated links and a hidden toctree.
docs/how-to/chiseling/index.rst	Adds meta description and a curated overview with hidden toctree for chiseling how-tos.

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