fixes: collab move, caldav abort, draft recovery, autobackup, test stabilization

- Collab: moving a shared card to a local bucket no longer deletes it
  (clear relay_uid before tombstone echo returns)
- CalDAV: abort sync on remote fetch failure instead of treating all
  local cards as remotely-deleted
- Editor: autobackup drafts to localStorage with restore prompt on
  re-open (skipped during tests)
- Cards POST: persist scratchpad and due_date (was dropped on create)
- Disable spellcheck/autocorrect on editor inputs
- Test runner: purge leftover __prefix__ cards/buckets + editor drafts
  before every run (cleans up from failed previous runs)
- Stabilize mark-done, group-delete, undo-body tests with poll loops

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/CalDavSync.php

@@ -381,11 +381,16 @@ class CalDavSync
         $remoteMap = []; // uid -> event data (gets modified during reconciliation)
         $remoteAll = []; // uid -> event data (unmodified copy for tombstone lookups)
         $remoteEvents = [];
+        $fetchFailed = false;
         foreach ($urls['all'] as $calUrl) {
             $calSlug = basename(rtrim($calUrl, '/'));
             $cal = $this->makeClient($calUrl);
             $res = $cal->request('REPORT', $calUrl, '<?xml version="1.0"?><c:calendar-query xmlns:d="DAV:" xmlns:c="urn:ietf:params:xml:ns:caldav"><d:prop><d:getetag/><c:calendar-data/></d:prop><c:filter><c:comp-filter name="VCALENDAR"><c:comp-filter name="VEVENT"/></c:comp-filter></c:filter></c:calendar-query>', ['Depth: 1']);
             $this->addLog('sync', null, null, 'fetch', $res['status'] == 207 ? 'ok' : 'error', "REPORT {$calSlug} HTTP {$res['status']}");
+            if ($res['status'] != 207) {
+                $fetchFailed = true;
+                continue;
+            }
             $events = $cal->listEvents();
             $this->addLog('sync', null, null, 'fetch', 'ok', count($events) . " events from {$calSlug}");
             $parseFail = 0;
@@ -403,6 +408,14 @@ class CalDavSync
             if ($parseFail) $this->addLog('sync', null, null, 'fetch', 'error', "{$parseFail} events failed to parse from {$calSlug}");
         }
 
+        // Abort on fetch failure — an incomplete remote list would make every
+        // local card look remotely-deleted and wipe them all. Better to sync
+        // nothing than to destroy local data on a flaky connection.
+        if ($fetchFailed) {
+            $this->addLog('sync', null, null, 'abort', 'error', 'remote fetch failed — skipping reconciliation to protect local data');
+            return $this->stats;
+        }
+
         $this->addLog('sync', null, null, 'fetch', 'ok', "total remote: " . count($remoteMap) . " events");
 
         // 3. Fetch local appointment cards — only #termin tagged or already synced