fix: anchored input patterns end at the last character (/D)

Without /D, "$" also matches before a trailing "\n", so "custom_meta_telefon\n",
a color setting "5\n" (stored as sent) or a whole reference followed by "\n"
passed VariableRef. Added /D to every ^...$ pattern that validates client or
admin input:
- VariableRef META_KEY, NUMBER, WHOLE (canonical/typeOf; Placeholders::field
  shares META_KEY)
- Cursor::decode, GuideRepository topic names (MCP input and filter keys)
- ExposurePolicy::sanitize ability keys and group ids, LogTab list filters

Not changed: Placeholders::PATTERN (runs on trim()), Warnings hex checks (hints
only), NodeSummary/AttrPathIndex/LogListTable (stored or Divi data, no client
input). Each fixed pattern has a test with a trailing "\n" that is rejected.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01At3V6SjwbMe6eMzVGW3Hs7

tests/Unit/Abilities/CursorTest.php

@@ -27,6 +27,12 @@ final class CursorTest extends TestCase
         self::assertNull(Cursor::decode(base64_encode('o:12;DROP')));
     }
 
+    /** "$" without /D also matches before a trailing newline – the cursor must end with the digits. */
+    public function testCursorWithTrailingNewlineIsRejected(): void
+    {
+        self::assertNull(Cursor::decode(rtrim(strtr(base64_encode("o:5\n"), '+/', '-_'), '=')));
+    }
+
     public function testLimitIsClamped(): void
     {
         self::assertSame(20, Cursor::limit(null));