The PluginConfig class extends CodeIgniter\Model which has its own set() method
for query building. Renaming get()/set() to getValue()/setValue() avoids this conflict.
Also fixed:
- batchSave() to use setValue() instead of set()
- Updated all callers in PluginManager and BasePlugin to use renamed methods
- Move plugin discovery to pre_system in Events.php (allows events to be registered before they fire)
- Add plugin existence check in disablePlugin()
- Add is_subclass_of check before instantiating plugin classes
- Fix str_replace prefix removal in getPluginSettings using str_starts_with + substr
- Add down() migration to drop table on rollback
- Fix saveSettings to JSON-encode arrays/objects
- Update README to use MailchimpPlugin as reference implementation
- Remove CasposPlugin examples from documentation
