M10: grayscale with Print as image prints on a driver that keeps no grayscale (#5806) (#5882)

* M10: grayscale with Print as image prints on a driver that keeps no grayscale (#5806)

With Print as image and grayscale, PdfCraft renders the pages as grey
pictures itself, yet the job still asked the driver for grayscale. A
driver that keeps no grayscale setting, Microsoft Print to PDF among
them, made craft-print refuse the job ("the printer's driver did not
retain the requested grayscale; nothing was sent"), so even the grey
pictures never printed. The job now asks the driver for grayscale only
when the pages aren't grey pictures already
(print::driver_needs_grayscale), in the dialog and in doc_print.

The print.grayscale parity note and the doc_print as_image description
say so, and the note names what is still missing: vector pages to such
a driver are refused rather than printed in colour.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* M10: the grey-pictures test checks that the pictures are grey too (#5806)

The test checked that grey pictures don't ask the driver for grayscale,
but not that the pictures are grey. A change that dropped grayscale from
the dialog's raster settings, while the job still skipped the driver,
would have printed in colour with the test passing. It now asserts both.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: austin62jake <340374338+austin62jake@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: FredApps <153173854+FredApps@users.noreply.github.com>

parity/acrobat-features.toml

@@ -8369,8 +8369,8 @@ milestone = "M10"
 status = "shipped"
 commands = ["print.dialog"]
 tools = ["doc_print"]
-evidence = ["crates/engine/src/tests.rs::printing_as_image_sends_pictures_instead_of_pages", "crates/ui-egui/tests/it/print.rs::print_as_image_is_an_advanced_choice_that_saves_pictures", "crates/automation/tests/it/automation.rs::doc_print_as_image"]
-notes = "asks the printer for monochrome (lp -o, and the Windows page settings as the job's); with Print as image the pictures themselves are rendered grey (Rec. 601 luma), so the print-ready PDF is grayscale too. Still missing against Acrobat: a grey conversion of the vector pages without rendering them."
+evidence = ["crates/engine/src/tests.rs::printing_as_image_sends_pictures_instead_of_pages", "crates/ui-egui/tests/it/print.rs::print_as_image_is_an_advanced_choice_that_saves_pictures", "crates/automation/tests/it/automation.rs::doc_print_as_image", "crates/automation/src/printing.rs::grey_pictures_dont_ask_the_driver_for_grayscale", "crates/ui-egui/src/workflows/print_ui.rs::grey_pictures_dont_ask_the_driver_for_grayscale"]
+notes = "asks the printer for monochrome (lp -o, and the Windows page settings as the job's); with Print as image the pictures themselves are rendered grey (Rec. 601 luma), so the print-ready PDF is grayscale too and the printer isn't asked for it: a driver that keeps no grayscale setting (Microsoft Print to PDF) prints them (#5806). Still missing against Acrobat: a grey conversion of the vector pages without rendering them, so vector pages to such a driver are refused rather than printed in colour."
 
 [[feature]]
 id = "print.print-as-image"