test: add comprehensive tests for --rasterizer option

Add test_rasterizer.py with tests covering:
- Basic rasterizer option validation ('auto', 'ghostscript', 'pypdfium')
- Rasterizer + --rotate-pages interaction
- PDFs with nonstandard MediaBox/TrimBox/CropBox
- Direct hook tests verifying plugins respect the option

Also fix pluggy parameter passing: make 'options' a required parameter
(no default) in the hookspec so pluggy forwards it to implementations.
Update test plugins and test_rotation.py to pass the new parameter.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/plugins/gs_raster_failure.py

@@ -24,9 +24,11 @@ def rasterize_pdf_page(
     raster_device,
     raster_dpi,
     pageno,
-    page_dpi=None,
-    rotation=None,
-    filter_vector=False,
+    page_dpi,
+    rotation,
+    filter_vector,
+    stop_on_soft_error,
+    options,
 ) -> Path:
     with patch('ocrmypdf._exec.ghostscript.run') as mock:
         mock.side_effect = raise_gs_fail
@@ -39,7 +41,8 @@ def rasterize_pdf_page(
             page_dpi=page_dpi,
             rotation=rotation,
             filter_vector=filter_vector,
-            stop_on_soft_error=True,
+            stop_on_soft_error=stop_on_soft_error,
+            options=options,
         )
         mock.assert_called()
         return output_file

tests/plugins/gs_raster_soft_error.py

@@ -29,6 +29,7 @@ def rasterize_pdf_page(
     rotation,
     filter_vector,
     stop_on_soft_error,
+    options,
 ) -> Path:
     with patch('ocrmypdf._exec.ghostscript.run') as mock:
         mock.side_effect = fail_if_stoponerror
@@ -42,6 +43,7 @@ def rasterize_pdf_page(
             rotation=rotation,
             filter_vector=filter_vector,
             stop_on_soft_error=stop_on_soft_error,
+            options=options,
         )
         mock.assert_called()
         return output_file