feat: tools and limits settings tabs

Adds Einstellungen → LIT MCP → Tools (direct/indirect/disabled per
ability, only ExposurePolicy-allowed modes offered) and → Limits
(upload size, log retention, snapshot count), wired into Plugin.php.

Ruling Q11b (carried from task 6): overview.md notes that direct
visibility is configurable; hints in src/ that name a tool which is
direct by default but can be switched to indirect (content-get,
content-query, content-types, post-publish, media-search) now use the
neutral "lit/<name> (direkt: lit-<name>)" form so they stay correct
after an admin override. lit/guide (always direct) and the
media-preview/-download DIRECT_ONLY tools are unaffected.

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

src/Integrations/Media/MediaGuard.php

@@ -35,7 +35,7 @@ final class MediaGuard
         if (! $attachment instanceof WP_Post || $attachment->post_type !== 'attachment') {
             return Errors::notFound(
                 sprintf('Medium %d nicht gefunden.', $attachmentId),
-                'ID prüfen; Medien über lit-media-search suchen.'
+                'ID prüfen; Medien über lit/media-search (direkt: lit-media-search) suchen.'
             );
         }