feat(cli): add CRUD helper, resource definitions, and help command

Resource-first CLI: `nc groups list`, `nc wirings get <id>`, etc.
Seven resources defined (groups, messaging-groups, wirings, users,
roles, members, sessions) with full column documentation that serves
as the single source of truth for help output and arg validation.

- CRUD helper auto-registers list/get/create/update/delete from
  declarative resource definitions with generic SQL
- Custom operations for composite-PK resources (roles grant/revoke,
  members add/remove)
- Access model: open (reads) / approval (writes) / hidden
- `nc help` lists resources; `nc <resource> help` shows fields
- Positional target IDs: `nc groups get <id>`
- Removed unused priority column from wirings

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/cli/commands/index.ts

@@ -1,4 +1,10 @@
-// Side-effect imports — each command file calls register() at top level.
-// Imported by src/index.ts on host startup so the registry is populated
-// before the CLI server accepts connections.
-import './list-groups.js';
+/**
+ * Command barrel — populates the registry before the CLI server starts.
+ *
+ * Resource definitions register their CRUD commands on import.
+ * Help commands are registered after resources are loaded.
+ */
+import '../resources/index.js';
+import { registerResourceHelpCommands } from './help.js';
+
+registerResourceHelpCommands();