Fix Paper shared connection access before plugin enable

[remdui]

What changed

• Keep every installed Paper plugin name in a dedicated policy-validation registry, including plugins that have not enabled yet or are temporarily disabled.
• Issue active caller identities only to enabled plugins; disabled plugins are known for configuration validation but receive no active capability identity.
• Retain installed-plugin knowledge across PluginDisableEvent while invalidating the disabled plugin's active identity and unregistering its database handles.
• Add regression coverage for startup ordering, disabled-plugin identity isolation, disable/re-enable lifecycle semantics, and full shutdown invalidation.

Root cause

Paper previously treated only already-enabled plugins as known. DataRegistry requests player_data_rw before ServerFeatures enables, so the valid shared_with: [ServerFeatures] declaration was rejected as referencing an unknown plugin. Velocity already discovers installed plugins before plugin work begins, which is why ProxyFeatures did not encounter the same failure.

Security model

Configuration knowledge and caller authority are deliberately separate:

• installed plugin names may appear in access policies regardless of enable order;
• only enabled plugins can bind an API identity;
• disabling a plugin invalidates its active identity and closes its registrations;
• DataProvider shutdown clears both registries.

Production configuration

player_data_rw:
  access:
    owner_plugin: DataRegistry
    shared_with:
      - ServerFeatures

This resolves both observed startup modes: DataRegistry no longer rejects the policy with InvalidConnectionAccessPolicyException, and ServerFeatures is no longer denied with ConnectionAccessDeniedException.