fix: neutral hint form for remaining client-facing tool mentions, Limits bounds accessor

Fix round 1 (task 10 review):
- FieldValidator's "unknown field" validation error (reaches the
  client via validation_failed's fields) and PostPresenter's
  DIVI_HINT (surfaced in the result's hints array) still named
  lit-content-types/lit-content-update as plain lit-<name>; converted
  both to the neutral "lit/<name> (direkt: lit-<name>)" form like the
  other hints from task 10. Re-grepped src/ for any other client-facing
  error/field/hints text naming a direct-by-default tool as lit-<name>
  (descriptions/schemas excluded per Q11c) - none left.
- Added Limits::bounds() (field => [min, max]) and made LimitsTab use
  it for the number inputs' min/max instead of a second, hardcoded
  copy of the same bounds.
- LimitsTab now shows a description note when the configured upload_mb
  exceeds wp_max_upload_size() (PHP's upload_max_filesize/post_max_size),
  since WordPress would refuse a larger upload before this limit ever
  applies.

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

src/Integrations/WordPress/Schema/FieldValidator.php

@@ -28,7 +28,8 @@ final class FieldValidator
             $key = (string) $key;
             $field = $definitions[$key] ?? null;
             if ($field === null) {
-                $errors[$key] = 'Unbekanntes Feld; verfügbare Felder über lit-content-types abrufen.';
+                $errors[$key] = 'Unbekanntes Feld; verfügbare Felder über lit/content-types (direkt: '
+                    . 'lit-content-types) abrufen.';
                 continue;
             }