fix: GlobalUsages finds every reference Divi renders, fail closed (F1, ruling P23)

Candidates come from one ID/status/type query: content with globalModule,
global_module or a JSON-escaped letter. Their content is read in chunks of
50 and parsed by UsageMatcher: Divi 5 openers are json-decoded (escaped keys
and values, leading zeros, any depth), and Divi 4 global_module attributes
are read in any quoting. An undecodable escaped opener counts as a possible
reference. Beyond 5000 candidates the rest count unread. The guide names
the formats and the wp_block parity. Also fixes the grammar of the
blocked-hidden count.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/Unit/Integrations/Divi/Library/GlobalEditsTest.php

@@ -342,7 +342,7 @@ final class GlobalEditsTest extends TestCase
         self::assertStringNotContainsString('1081', (string) wp_json_encode($data));
         self::assertToolError($refused, 'forbidden');
         self::assertStringNotContainsString('1081', $refused->get_error_message());
-        self::assertStringContainsString('nicht lesen darf', $refused->get_error_message());
+        self::assertStringContainsString('1 Eintrag, den dieses Konto nicht lesen darf', $refused->get_error_message());
         self::assertSame([], $this->saved);
     }