[cross-repo from server#284] Conformance blocker: make v1 to v2 migration guarantees measurable against current artifacts (#700)

Author: durable-workflow-ops

docs/architecture/platform-conformance-suite.md

@@ -90,6 +90,11 @@ column lists it *and* the category status is not `provisional`.
 Provisional categories ship an advisory result (warn but do not fail);
 they become required when promoted to `stable` in a later suite version.
 
+Migration runtime coverage is intentionally absent from suite version
+12. It becomes a fixture category only after the docs-site static
+contract and public scenario manifest publish together; until then,
+implementations do not fail conformance for missing migration scenarios.
+
 ### Signals and queries runtime contract
 
 The `signal_query_runtime_contract` category is stable and load-bearing.

tests/Unit/V2/PlatformConformanceSuiteTest.php

@@ -165,6 +165,35 @@ public function testEveryFixtureCategoryAuthorityDocIsACustomerResolvableUrl():
         }
     }
 
+    public function testMigrationRuntimeContractIsDeferredUntilPublicScenarioManifestPublishes(): void
+    {
+        $manifest = PlatformConformanceSuite::manifest();
+
+        $this->assertSame(
+            12,
+            $manifest['version'],
+            'the workflow mirror must stay aligned with the currently published platform conformance contract',
+        );
+        $this->assertArrayNotHasKey(
+            'migration_runtime_contract',
+            $manifest['fixture_catalog'],
+            'migration conformance becomes a fixture category only after its public scenario manifest exists',
+        );
+        $this->assertNotContains(
+            'migration_runtime_contract',
+            $manifest['pass_fail_rules']['stable_runtime_scenario_coverage']['applies_to_categories'],
+            'missing migration scenarios must not be part of stable runtime coverage while the source manifest is unpublished',
+        );
+
+        foreach ($manifest['targets'] as $name => $target) {
+            $this->assertNotContains(
+                'migration_runtime_contract',
+                $target['required_fixture_categories'],
+                "$name must not require migration conformance before the public scenario manifest is published",
+            );
+        }
+    }
+
     public function testMcpDiscoveryCategoryNamesCurrentReferenceSurface(): void
     {
         $manifest = PlatformConformanceSuite::manifest();