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>

modules/helpdesk/lib/Module/Helpdesk/Service/SystemRecommendationEngine.php

@@ -244,7 +244,7 @@ class SystemRecommendationEngine
         return [
             'recommendations' => array_slice($deduped, 0, $maxItems),
             'meta' => [
-                'applied_rules' => array_values(array_keys($appliedRulesMap)),
+                'applied_rules' => array_keys($appliedRulesMap),
                 'max_items' => $maxItems,
                 'escalation_data_available' => $escalationAvailable,
             ],
@@ -379,9 +379,6 @@ class SystemRecommendationEngine
         $openTickets = [];
 
         foreach ($tickets as $ticket) {
-            if (!is_array($ticket)) {
-                continue;
-            }
 
             $state = trim((string) ($ticket['Ticket_State'] ?? ''));
             if (in_array($state, self::CLOSED_TICKET_STATES, true)) {