Properly cleanup SQLite persistence artifacts

[viralpraxis]

CI errors are reproducible locally:

$ env POSTGRES_URL=postgres://postgres:postgres@localhost:5432 DB=postgres BUNDLE_GEMFILE=gemfiles/rails8.gemfile bundle exec rspec

<snip>/lib/active_record/connection_adapters/sqlite3/database_statements.rb:105:in 'SQLite3::Statement#step': SQLite3::IOException: disk I/O error (ActiveRecord::StatementInvalid)
	from <snip>/lib/active_record/connection_adapters/sqlite3/database_statements.rb:105:in 'ActiveRecord::ConnectionAdapters::SQLite3::DatabaseStatements#perform_query'
	from <snip>/lib/active_record/connection_adapters/abstract/database_statements.rb:571:in 'block (2 levels) in ActiveRecord::ConnectionAdapters::DatabaseStatements#raw_execute'
	from <snip>/lib/active_record/connection_adapters/abstract_adapter.rb:1081:in 'block in ActiveRecord::ConnectionAdapters::AbstractAdapter#with_raw_connection'
	from /home/viralpraxis/.asdf/installs/ruby/3.4.7/lib/ruby/gems/3.4.0/gems/activesupport-8.1.1/lib/active_support/concurrency/null_lock.rb:9:in 'ActiveSupport::Concurrency::NullLock#synchronize'
	from <snip>/lib/active_record/connection_adapters/abstract_adapter.rb:1050:in 'ActiveRecord::ConnectionAdapters::AbstractAdapter#with_raw_connection'
	from <snip>/lib/active_record/connection_adapters/abstract/database_statements.rb:570:in 'block in ActiveRecord::ConnectionAdapters::DatabaseStatements#raw_execute'

I have no idea what changed on the SQLite's side but seems like we have to cleanup WAL and shared-memory files:

$ ls tmp
testdb2  testdb2-shm  testdb2-wal

$ sqlite3 --version
3.51.0 2025-11-04 19:38:17 fb2c931ae597f8d00a37574ff67aeed3eced4e5547f9120744a-experimental (64-bit)