feat(ai-outfit): auto-append output requirements to prompt (§19.6)

- core/ai_outfit: OUTPUT_REQUIREMENTS constant + build_output_requirements();
  render_prompt(template, task, resolution=None) appends the block when a
  resolution is given; generate_outfit_image passes the current resolution.
- ai_outfit_panel: inline preview now uses render_prompt/build_output_requirements
  with the selected resolution and refreshes when the resolution combo changes,
  so the preview equals what is actually sent.
- tests: +3 cases (tail with resolution, none without, helper empty/filled);
  updated the success test for the appended tail. Full suite (12 files) green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/widgets/ai_outfit_panel.py

@@ -258,6 +258,7 @@ class AiOutfitPanel(QWidget):
         self._retry_count.setRange(0, 10)
         self._resolution = QComboBox()
         self._resolution.addItems(_RESOLUTIONS)
+        self._resolution.currentIndexChanged.connect(self._refresh_preview)
         self._quality = QComboBox()
         self._quality.addItems(_QUALITIES)
 
@@ -472,17 +473,19 @@ class AiOutfitPanel(QWidget):
     def _refresh_preview(self):
         if not hasattr(self, "_preview_view"):
             return
+        from core.ai_outfit import build_output_requirements, render_prompt
         template = self._prompt_edit.toPlainText()
         self._preview_warn.setVisible("{title}" not in template)
         if "{title}" not in template:
             self._preview_warn.setText("⚠ 话术缺少 {title} 占位符")
+        # Mirror what actually gets sent: append the output-requirements block
+        # for the currently selected resolution (docs/11 §7.1).
+        resolution = self._resolution.currentText() if hasattr(self, "_resolution") else None
         task = self._sample_combo.currentData() if hasattr(self, "_sample_combo") else None
         if task is None:
-            self._preview_view.setPlainText(template)
+            self._preview_view.setPlainText(template + build_output_requirements(resolution))
         else:
-            rendered = template.replace("{title}", task.title).replace(
-                "{product_id}", task.product_id)
-            self._preview_view.setPlainText(rendered)
+            self._preview_view.setPlainText(render_prompt(template, task, resolution))
 
     # -- run control ----------------------------------------------------