fix(docs): separated the introduction sidebar

[nickfrosty]

Problem

The Solana docs sidebars restructure for #26699

Summary of Changes

• segmented the "introduction" section sidebar from the global sidebar
• moved the "wallet-guide" into the introduction section
• moved the "command line wallets" section into the command line section of the global sidebar
• updated docs home page card "Learn how Solana works" to link to the "introduction" pages

Work in Progress for: #26699

Screenshot of the new "introduction" section sidebar:

[stale[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[nickfrosty]

Bump to prevent being deleted

[jacobcreech]

@nickfrosty If I am on any page that is outside of the introduction, how do I access the intro? I was having a difficult time finding it from /developing/programming-model/overview

[nickfrosty]

With this PR and the other sidebar restructure PRs, there are only a few ways to get to this section:

• home page
• footer link
• any of the random places there is an internal link to the page (which for the intro section, I don't think there are many, if not any)

[stale[bot]]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.