`Primary` doesn't trigger migrations as it should

• Removing a Primary declaration does not cause the uniqueness constraint or primary key to be dropped

  <<<
  User
    name Text
    Primary name
  ====
  User
    name Text
  >>>
  

  This should result in a migration that drops the primary key. It does not.

• Adding a Primary declaration to an existing non-unique column isn't considered an unsafe migration by any of the current backends. It fails on sqlite at runtime.

Start by tracing how migration changes for Primary declarations are generated and how unsafe migrations are checked across the current backends. Reproduce both examples, including the SQLite case, and inspect the generated migration and safety result. Done means removing Primary drops the primary key or uniqueness constraint, while adding it to a non-unique column is reported as unsafe.