refactor: fix all 105 PHPStan 2 strict type findings across core and modules

Resolve all non-false-positive PHPStan 2 findings, reducing the baseline
from 486 to 382 entries (only unused-public false positives remain).

Categories fixed:
- Remove 39 redundant type checks (is_string, is_array, is_object, method_exists)
- Remove 12 no-op array_values() on already-sequential lists
- Simplify 13 null-coalesce on guaranteed offsets
- Remove 8 always-true instanceof checks
- Replace 12 redundant test assertions (assertTrue(true) → addToAssertionCount)
- Simplify 6 unnecessary nullsafe operators (?-> → ->)
- Fix 6 always-true !== '' comparisons
- Fix remaining: unset.offset, return.unusedType, staticMethod narrowing

53 files changed across core/, modules/, pages/, and tests/.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/Service/Access/UiAccessService.php

@@ -53,14 +53,10 @@ final class UiAccessService
                 continue;
             }
 
-            if (!is_array($definition)) {
-                $resolved[$key] = false;
-                continue;
-            }
 
             $ability = $definition['ability'];
             $context = [];
-            if (array_key_exists('context', $definition) && is_array($definition['context'])) {
+            if (array_key_exists('context', $definition)) {
                 $context = $this->normalizeContext($definition['context']);
             }
             $resolved[$key] = $this->allow($actorUserId, $ability, [
@@ -113,7 +109,7 @@ final class UiAccessService
     private function normalizeContext(array $context): array
     {
         $normalized = $this->normalizeValue($context);
-        return is_array($normalized) ? $normalized : [];
+        return $this->normalizeValue($context);
     }
 
     private function normalizeValue(mixed $value): mixed