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/Support/helpers/request.php

@@ -101,9 +101,6 @@ function requestNormalizeSafeInternalTarget(string $target, int $maxDepth = 5):
 
     $queryParams = [];
     parse_str((string) ($safeParts['query'] ?? ''), $queryParams);
-    if (!is_array($queryParams)) {
-        $queryParams = [];
-    }
     $nestedReturnTarget = requestExtractNestedReturnValue($queryParams['return'] ?? null);
     unset($queryParams['return']);
     $query = http_build_query($queryParams);
@@ -185,9 +182,6 @@ function requestPathWithReturnTarget(string $path, string $returnTarget = ''): s
     }
     $queryParams = [];
     parse_str((string) ($parts['query'] ?? ''), $queryParams);
-    if (!is_array($queryParams)) {
-        $queryParams = [];
-    }
     unset($queryParams['return']);
     $queryParams['return'] = $normalizedReturnTarget;
     $query = http_build_query($queryParams);