HTTP: prefer pip-system-certs/certifi_win32 bundle; use init-time verify in retries; add tests

cmdlet/convert_file.py

@@ -128,12 +128,24 @@ def _doc_convert(input_path: Path, output_path: Path) -> bool:
         return False
 
     target_fmt = output_path.suffix.lstrip(".").lower() or "pdf"
+    extra_args = []
+
+    if target_fmt == "pdf":
+        tectonic_path = shutil.which("tectonic")
+        if not tectonic_path:
+            log(
+                "tectonic is required for PDF output; install with `pip install tectonic`",
+                file=sys.stderr,
+            )
+            return False
+        extra_args = ["--pdf-engine=tectonic"]
 
     try:
         pypandoc.convert_file(
             str(input_path),
             to=target_fmt,
             outputfile=str(output_path),
+            extra_args=extra_args,
         )
     except OSError as exc:
         log(f"pandoc is missing or failed to run: {exc}", file=sys.stderr)
@@ -163,7 +175,7 @@ CMDLET = Cmdlet(
     detail=[
         "Allows video↔video, audio↔audio, image↔image, doc↔doc, and video→audio conversions.",
         "Disallows incompatible conversions (e.g., video→pdf).",
-        "Uses ffmpeg for media and pypandoc-binary (bundled pandoc) for document formats (mobi/epub→pdf/txt/etc).",
+        "Uses ffmpeg for media and pypandoc-binary (bundled pandoc) for document formats (mobi/epub→pdf/txt/etc); PDF output uses the tectonic LaTeX engine when available.",
     ],
 )