feat: media upload by URL and base64 with whitelist and size limit

MediaImporter streams URL imports via wp_safe_remote_get with limit_response_size,
checks Content-Length, intersects the MIME whitelist with get_allowed_mime_types and
validates real content; base64 is size-checked before decoding. Server-side failures
are write_failed; a failed alt text deletes the new attachment again (or partial_write).
MediaUploads is the shared permission/result helper of both upload abilities.

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

src/Integrations/Media/MediaIntegration.php

@@ -10,8 +10,8 @@ use LIT\MCP\Integrations\WordPress\Schema\ContentSchema;
 use LIT\MCP\Limits;
 
 /**
- * Media library tools (spec §6.3). Always available. $log and $limits are used by the
- * write tools that follow (upload, update, delete).
+ * Media library tools (spec §6.3). Always available. $log and $limits serve the write
+ * tools (upload now, update and delete to follow).
  */
 final class MediaIntegration implements Integration
 {
@@ -33,11 +33,15 @@ final class MediaIntegration implements Integration
     {
         $presenter = new MediaPresenter();
         $finder = new MediaUsageFinder(fn (): array => $this->schema->mediaFieldKeys());
+        $importer = new MediaImporter($this->limits);
+        $uploads = new MediaUploads($presenter, $this->log, $this->schema);
 
         return [
             new MediaSearchAbility($presenter, $finder),
             new MediaGetAbility($presenter, $finder),
             new MediaPreviewAbility(),
+            new MediaUploadFromUrlAbility($importer, $uploads),
+            new MediaUploadAbility($importer, $uploads, $this->limits),
             new MediaDownloadAbility($this->limits),
         ];
     }