fix(2meet-data-optimizer): report entity group name collisions instead of silently dropping

- register_group() keeps the first definition but records a field diff (added/removed/changed) when the same entity/group is re-registered differently; identical re-registration stays silent
- Surface collisions via Site Health (wpdo_entity_group_collisions), the admin Doctor tab, and wp wpdo doctor; warning log throttled to once a day
- Verify: EntityRegistryCollisionTest (7); core unit 613 / integration 432, HP 141/49, WC 10/22 OK
- PR: PR-017

cli/class-tmdo-cli.php

@@ -330,6 +330,25 @@ class TMDO_CLI {
 			WP_CLI::log( '  [OK] Crypto key derivable (AUTH_KEY / SECURE_AUTH_SALT present)' );
 		}
 
+		// ── Entity group name collisions ─────────────────────────────────────────
+		$collisions = TMDO_Entity_Registry::get_collisions();
+		if ( empty( $collisions ) ) {
+			WP_CLI::log( '  [OK] No entity group name collisions' );
+		}
+		foreach ( $collisions as $c ) {
+			WP_CLI::warning(
+				sprintf(
+					'  [COLLISION] %s/%s registered twice with different fields (second ignored) — added: %s; removed: %s; changed: %s',
+					$c['entity_type'],
+					$c['group'],
+					implode( ', ', $c['added'] ) ?: '-',
+					implode( ', ', $c['removed'] ) ?: '-',
+					implode( ', ', $c['changed'] ) ?: '-'
+				)
+			);
+			$all_ok = false;
+		}
+
 		// Check recent errors.
 		$errors = TMDO_Logger::get_recent( '', 5 );
 		if ( ! empty( $errors ) ) {