Track removal of the deprecated WP_SQLite_Driver API

Context

WP_MySQL_On_SQLite is now the primary PDO-compatible API, but the deprecated WP_SQLite_Driver class remains temporarily for backward compatibility.

Remove the compatibility class only after maintained dependent projects no longer instantiate, extend, type against, or otherwise depend on WP_SQLite_Driver or its legacy constructor and result API.

Known dependent projects

• WordPress/sqlite-database-integration production consumers (WordPress integration and MySQL proxy) use WP_MySQL_On_SQLite directly after #449.
• Automattic/wp-cli-sqlite-command — tracked in Automattic/wp-cli-sqlite-command#34.
• WordPress/reprint — the exporter detects and wraps WP_SQLite_Driver.
• WordPress/desktop-mode — the phpMyAdmin SQLite adapter constructs WP_SQLite_Driver.
• WordPress/wordpress-playground — the PHP 5.2 compatibility patch references and modifies WP_SQLite_Driver.
• Automattic/markdown-database-integration — WP_Markdown_Driver extends WP_SQLite_Driver, and the write engine type-hints it.
• lucatume/wp-browser — its vendored SQLite integration constructs and branches on WP_SQLite_Driver.
• Inventory non-public/internal consumers, including WordPress Studio integrations.
• TODO: Add other known maintained dependent projects.

Public code search also finds many repositories containing vendored plugin copies or application snapshots. Re-run the search before removal, but do not treat every copied release as a separately coordinated dependency.

Removal criteria

• Every maintained dependent project above has migrated away from WP_SQLite_Driver.
• Re-run public GitHub code search and internal code search for WP_SQLite_Driver; classify any remaining maintained consumers.
• Decide and communicate the removal release and migration window.
• Remove class-wp-sqlite-driver.php, its loader entry, and compatibility-only tests.
• Update API documentation, migration guidance, and release notes.
• Run the full SQLite driver, WordPress integration, MySQL proxy, and relevant downstream test suites without the compatibility class.

Start by reviewing the listed dependent projects and the linked migration issue, then rerun public and internal searches for WP_SQLite_Driver. Track maintained consumers and their migration status before deciding the removal release and window. Done means the criteria are met, class-wp-sqlite-driver.php, its loader entry, and compatibility-only tests are removed, documentation and release notes are updated, and the specified test suites pass.