Use the deferred state-version helper mode for programs.password-store.settings
so explicit empty and explicit legacy values silence the warning correctly,
while partial legacy-era settings still inherit PASSWORD_STORE_DIR until the
user resolves the migration.
Add integration coverage for password-store and pass-secret-service to verify
legacy, explicit empty, explicit legacy, and partial-settings behavior.
Signed-off-by: Austin Horstman <khaneliman12@gmail.com>
