Debug: add image preview (first page) with PyMuPDF/pdfium; return PDF path from debug flows; chain .then to render image

app.py

@@ -2081,7 +2081,7 @@ def debug_compile_output_zip():
     except Exception as e:
         logs.append(f"⚠️ preview failed: {e}")
         _write_logs(LOG_PATH, logs)
-        return f"<div>Compiled but preview failed: {e}</div>"
+        return f"<div>Compiled but preview failed: {e}</div>", None
 
 def _find_last_pipeline_zip():
     try:
@@ -2102,7 +2102,7 @@ def _find_last_pipeline_zip():
         return None
 
 def debug_compile_last_pipeline_zip():
-    """Find the most recent runs/*/output.zip from pipeline, compile, and preview the PDF."""
+    """Find the most recent runs/*/output.zip from pipeline, compile, and return preview HTML + PDF path."""
     logs = [f"🐞 Debug(last-pipeline-zip) at {_now_str()}"]
     last_zip = _find_last_pipeline_zip()
     if not last_zip:
@@ -2117,7 +2117,7 @@ def debug_compile_last_pipeline_zip():
                 logs.append(f"❌ Auto-stage failed: {e}")
                 return "<div style='color:#b00'>No recent pipeline output.zip found and auto-stage failed.</div>"
         else:
-            return "<div style='color:#b00'>No recent pipeline output.zip found under runs/.</div>"
+            return "<div style='color:#b00'>No recent pipeline output.zip found under runs/.</div>", None
 
     # Prepare workspace
     run_id, WORK_DIR, LOG_PATH, _ = _prepare_workspace(logs)
@@ -2134,7 +2134,7 @@ def debug_compile_last_pipeline_zip():
     except Exception as e:
         logs.append(f"❌ unzip failed: {e}")
         _write_logs(LOG_PATH, logs)
-        return "<div style='color:#b00'>Unzip failed.</div>"
+        return "<div style='color:#b00'>Unzip failed.</div>", None
 
     # Locate tex
     tex_path = None
@@ -2150,7 +2150,7 @@ def debug_compile_last_pipeline_zip():
     if tex_path is None:
         logs.append("❌ No .tex file found in last pipeline zip")
         _write_logs(LOG_PATH, logs)
-        return "<div style='color:#b00'>No .tex found in last pipeline zip</div>"
+        return "<div style='color:#b00'>No .tex found in last pipeline zip</div>", None
 
     # Ensure local fonts and theme precedence (same as other debug path)
     try:
@@ -2186,7 +2186,8 @@ def debug_compile_last_pipeline_zip():
             "<div style='color:#b00'><b>Compile failed.</b></div>"
             + "<pre style='white-space:pre-wrap;background:#f7f7f8;padding:8px;border-radius:6px'>"
             + "\n".join(logs)
-            + "</pre>"
+            + "</pre>",
+            None,
         )
     try:
         b64 = base64.b64encode(pdf_path.read_bytes()).decode("utf-8")