Add the get_permissions plugin hook (contract 0.10.0)

Plugins declare their own RBAC permissions instead of core accumulating
them: 36 permissions moved out of the core catalog into the 9 owning
plugins (core keeps the 19 its own blueprints enforce). The catalog is
resolved dynamically (core + enabled plugins) and feeds the roles grid,
the token scope picker and ceiling, and flask seed permissions;
installing or enabling a plugin seeds its permissions automatically. A
disabled plugin drops out of the assignable catalog while existing role
links keep working. New plugins - bundled or external - now bring their
permissions with zero core edits.

781 tests pass; live-verified with a machines.edit-scoped token.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

plugins/knowledgebase/plugin.py

@@ -72,3 +72,12 @@ class KnowledgeBasePlugin(BasePlugin):
                 'section': 'information',
             },
         ]
+
+    def get_permissions(self) -> List:
+        """Return the RBAC permissions this plugin owns."""
+        return [
+            ('kb.view', 'View knowledge base', 'knowledgebase'),
+            ('kb.create', 'Create KB articles', 'knowledgebase'),
+            ('kb.edit', 'Edit KB articles', 'knowledgebase'),
+            ('kb.delete', 'Delete KB articles', 'knowledgebase'),
+        ]