feat(images): retry Cloudflare NSFW-blocked prompts with a sanitized fallback

Cloudflare's Workers AI FLUX.1 schnell content filter sometimes rejects
peptide-comic prompts as NSFW (HTTP 400, errors[].code === 3030). On
2026-04-20 this produced a silent publish-without-featured-image for
post #650 ("Semaglutide vs Tirzepatide") — the LLM-rewritten scene
tripped the filter and we had no recovery path.

New behaviour: on a 3030 response, the Cloudflare provider throws a
typed PRAutoBlogger_Image_NSFW_Blocked exception. The batch wrapper
catches it and tags the per-slot result with
`error_type: nsfw_blocked`. Image_Pipeline hands the results to a new
PRAutoBlogger_Image_NSFW_Retry helper, which reruns the blocked slot
once with a sanitized fallback prompt (title + style suffix, no LLM
rewrite). On success the retry result replaces the error entry; on a
second block, a WARNING is logged and the pipeline publishes without
that image — same terminal behaviour we had before, just explicit.

Files:

- New providers/class-image-nsfw-blocked.php — typed exception.
- providers/class-cloudflare-image-support.php — is_nsfw_error() +
  throw_if_nsfw() helpers.
- providers/class-cloudflare-image-provider.php — calls throw_if_nsfw
  inside the 4xx branch; batch catches the typed exception and marks
  the result with error_type.
- core/class-image-prompt-builder.php — new public build_fallback_prompt
  shim so the retry layer can reach the rule-based fallback without
  going through the LLM path.
- New core/class-image-nsfw-retry.php — single-shot retry helper.
- core/class-image-pipeline.php — invokes the retry between batch
  completion and per-slot processing.
- admin/class-settings-fields-extended.php — new toggle
  `prautoblogger_image_nsfw_retry` (default on) in the Images section.

Tests:

- CloudflareImageProviderTest — 3030 response throws NSFW exception;
  batch tags the per-slot result with `error_type: nsfw_blocked`.
- ImagePipelineTest — retry succeeds when provider returns a good
  result on the second call; retry is skipped when the setting is off.

Cost impact: worst-case an extra Cloudflare call per NSFW-blocked slot
(~$0.000834). Current incidence ~2% of generations; ~+$0.00002 per
generation amortized. Immaterial.

Uninstall: new option covered by the existing prautoblogger_% LIKE
sweep in uninstall.php.

Part of the v0.8.0 image bundle (issues from thread image-mime-bug).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

includes/core/class-image-pipeline.php

@@ -138,6 +138,12 @@ class PRAutoBlogger_Image_Pipeline {
 			return $result;
 		}
 
+		// Single-shot retry for any slot the provider flagged as NSFW-blocked.
+		if ( PRAutoBlogger_Image_NSFW_Retry::is_enabled() ) {
+			( new PRAutoBlogger_Image_NSFW_Retry( $this->provider, $this->prompt_builder ) )
+				->retry_blocked_slots( $post_id, $batch_requests, $batch_results, $captions, $article_data, $source_data );
+		}
+
 		// Process Image A result.
 		$this->process_image_a( $post_id, $batch_results, $captions, $result );