[Documentation] Add WP-CLI database connection troubleshooting to Blueprints

[fellyph]

This issue proposes adding a new troubleshooting section and a corresponding example to the Blueprints documentation to address an issue found by @jonathanbossenger and solved by @bgrgicak when he was running WP-CLI commands on mounted WordPress Playground sites.

Problem

Users attempting to run wp-cli commands (e.g., wp plugin list) on a WordPress Playground instance that uses --mount-before-install often encounter an "Error establishing a database connection." It occurs because the SQLite database integration plugin, which Playground typically loads internally, isn't persisted in the mounted directory.

Proposed Changes

Add a new subsection to /blueprints/troubleshoot-and-debug and a new example to /blueprints/examples:

• Section Title: WP-CLI: Error Establishing a Database Connection on Mounted Sites: Explain the problem and provide the Blueprint solution (installing, copying db.php, and activating the sqlite-database-integration plugin). Include a full Blueprint example and CLI command to demonstrate.
• Section Title: Running WP-CLI on Mounted Sites: A concise Blueprint example showing the steps to enable wp-cli on mounted sites, with a link to the detailed explanation in the troubleshooting section.

[bgrgicak]

If we are working on a SQL section, here are a few useful FAQs from Studio that could be helpful for Playground users.

• How can I manage the Studio site’s SQLite database?
  • For this to work in Playground, users would need to mount the /wordpress/wp-content/database folder from Playground on their machine.
• How can I use Studio with the MySQL server of my choice?
  • For this to work with Playground users would need to mount wp-config.php from their machine into Playground.