PDF export: a set Don't Include Profiles removes image color profiles

When Profile inclusion is set to Don't Include Profiles (`profiles:
"none"`), gray, RGB and CMYK images are written in device color spaces
without their ICC profiles, and a JPEG that is kept as is loses its
APP2 ICC_PROFILE segments. PDF/A-2b, PDF/X-3 and PDF/X-4 keep tagging
their images.

Leaving the setting out keeps the earlier output. `profiles` now
serializes as null when not set, `"default"` clears a preset's value,
and Save PDF > Output lists Default first. Presets and stored settings
saved earlier hold `"profiles": "none"`, so exports from them now drop
image profiles.

docs/mcp.md

@@ -5917,7 +5917,11 @@ for its colour mode). `profiles` (`all`, `destination`, or `taggedSource` for a
 the document's CMYK profile, RGB as sRGB, grey with the sRGB tone curve (PDF/A, PDF/X-3 and PDF/X-4 files are
 always tagged, whatever `profiles` says). A CMYK image that keeps its numbers carries the CMYK profile it embeds
 with `all` and `taggedSource`, and in PDF/A, PDF/X-3 and PDF/X-4 unless `profiles` is `destination`; PDF/X-1a
-images are always untagged CMYK. `outputIntent` embeds a profile as the file's
+images are always untagged CMYK. Left unset (the default; `"default"` unsets it over a preset, while `null` keeps the
+preset's value), `profiles` writes device colours and gray and RGB images keep the profiles they carry (not in
+PDF/X-1a). Set to `none`, it also writes every image without the profile it carries, and a JPEG kept as it is without
+its `ICC_PROFILE` segments, its other segments and compressed samples unchanged; PDF/A, PDF/X-3 and PDF/X-4 files keep
+the profiles they tag images with. The Save PDF dialog lists the unset value as Default. `outputIntent` embeds a profile as the file's
 `/GTS_PDFX` output intent with `outputCondition`, `outputConditionId` and `registry`, and `trapped` sets `/Trapped`
 (PDF/A files keep their own output intent). Type is written as selectable, searchable text in embedded subset fonts
 with a ToUnicode map (fonts whose licence forbids embedding stay outlines, with a warning); `advanced: {outlineText:

docs/target-app-parity.md

@@ -1930,6 +1930,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - The pixels of a PNG, JPEG, GIF or WebP file that Place decodes to check them are kept in the image store the renderers share, so the canvas's first frame with the placed image draws them without decoding the file again on the UI thread: File › Place, a file dropped on the canvas, a click or drag of the place cursor, `file.place`, and Paste of such an image. A CMYK JPEG is still decoded when it is first drawn (`crates/ui-egui/src/placing.rs`, `crates/render/src/tests.rs`).
   - A photo whose EXIF orientation turns or flips it (a camera held upright or upside down) is placed and opened upright, as it was taken; the image is stored as it is seen (#4284). A quarter turn swaps the resolution's axes, so the image keeps its physical size. TIFFs read without the image decoder (grayscale with extra channels, CCITT Group 3, CMYK with one plane per ink) follow their Orientation tag too, and a turned CMYK JPEG or TIFF keeps its inks, at the 8 or 16 bits the file has, as a CMYK TIFF.
   - PDF export writes a CMYK image that keeps its numbers in an `ICCBased` color space holding, byte for byte, the CMYK profile the image carries (a CMYK TIFF's tag 34675, or a CMYK JPEG's `ICC_PROFILE` APP2 segments) when `output.profiles` is `all` or `taggedSource`, and in PDF/A-2b, PDF/X-3 and PDF/X-4 unless it is `destination` ([the help page](https://helpx.adobe.com/illustrator/desktop/save-and-export/export-files-to-different-formats/pdf-marks-bleeds-and-color-output-options.html)). This covers a CMYK JPEG embedded as it is, one the Compression settings resample or compress again, a TIFF written again, and an image written with its mask as its soft mask. With `none`, and in PDF/X-1a, the image is DeviceCMYK and a JPEG's own profile is left out, so PDF/X-1a export writes a CMYK JPEG that carries a profile. Pixels the Output settings convert are never tagged with the profile of their old numbers. A profile tags an image only when its size, signature, class, CMYK color space and tag table are well formed and it is at most 16 MiB (VectorCraft's own limit). Transparency in a tagged CMYK document blends in the document's CMYK profile; when the file holds no space of that profile it blends in DeviceCMYK, or keeps its RGB space in PDF/A, and never in an image's own profile (`crates/pdf/src/tests/cmykimages.rs`, `export::writer::tests`).
+  - PDF export with `output.profiles` set to `none` (Don't Include Profiles) writes no image with the ICC profile it carries, as [the help page](https://helpx.adobe.com/illustrator/desktop/save-and-export/export-files-to-different-formats/pdf-marks-bleeds-and-color-output-options.html) describes for that setting: gray and RGB PNG, JPEG and TIFF images embedded as they are, resampled or compressed again, and CMYK JPEG images. A JPEG kept as it is loses its `ICC_PROFILE` APP2 segments, its other segments and compressed samples unchanged. PDF/A-2b, PDF/X-3 and PDF/X-4 files keep the profiles they tag images with. Left unset (the default, `"default"`, listed as Default in Save PDF), the setting writes device colors while gray and RGB images keep their profiles, as before; that default is VectorCraft's own rule (`a_set_dont_include_profiles_removes_image_profiles`, `a_set_dont_include_profiles_takes_a_cmyk_jpegs_profile_out`).
   - PDF import keeps the CMYK profile of an image in a four-component `ICCBased` color space, whose stream holds the profile ([ISO 32000-1, §8.6.5.5](https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf#page=157)), byte for byte with the image's ink amounts, so PDF export can write the image in it again. A CMYK TIFF carries it as tag 34675, whatever the image's Decode array and bit depth ([ICC.1:2010, Annex B](https://www.color.org/specification/ICC1v43_2010-12.pdf)). A CMYK JPEG kept as it is carries it in `ICC_PROFILE` APP2 segments in place of a profile of its own, with its compressed samples unchanged, and one whose segments can't hold it is stored as a CMYK TIFF carrying it. A profile that isn't well formed, isn't of CMYK colors or is over 16 MiB (VectorCraft's own limit) leaves the image's inks as they are, untagged. DeviceCMYK and DeviceN images carry no profile, and a CMYK TIFF's tag 34675 is read up to 16 MiB. EPS and PostScript import does not keep one: PostScript defines no `ICCBased` profile stream (`crates/pdf/src/tests/cmykimages.rs`, `cmyk::tests`).
   - An image that Open and Place store again keeps the ICC profile its file embeds and its 16-bit samples. A turned PNG, JPEG, WebP or TIFF stored as PNG, and a TIFF the image decoder reads, keep their gray or RGB samples at 8 or 16 bits with their gray or RGB profile in the PNG's `iCCP` chunk ([PNG specification, iCCP](https://www.w3.org/TR/png-3/#11iCCP)). A CMYK TIFF stored with one plane per ink and a turned CMYK JPEG or TIFF keep their CMYK profile as TIFF tag 34675, a JPEG's put together from all its APP2 segments ([ICC image-format guide](https://github.com/InternationalColorConsortium/iccDEV/blob/master/iccdev-mcp/docs/icc-format-guide.md)). A profile whose color space differs from the stored samples' is left out. The profile is kept in the stored image; how CMYK inks are drawn and exported to PDF does not change (`crates/engine/src/cmd/fileio/tests.rs`).
   - PDF export writes a stored gray or RGB TIFF in an `ICCBased` color space that holds the gray or RGB profile of its tag 34675, at 16 bits a sample from PDF 1.5 on and 8 before, with its alpha as a soft mask only when some pixel is not opaque ([ISO 32000-1, §8.6.5.5](https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf#page=157)). A gray or RGB image, a PNG included, that the Compression settings resample or compress with JPEG keeps its profile too, and gray pixels in an RGB profile stay RGB. Pixels the Output settings convert, a profile whose color space differs from the samples', and a malformed profile, a PNG's or JPEG's kept as it is included, are written without it; such a JPEG keeps its JPEG data. PDF/X-1a allows no ICC-based color spaces, so there a gray image with a gray profile, kept as it is, resampled or compressed with JPEG, is written in DeviceGray without the profile, a JPEG kept as JPEG with its JPEG data unchanged, and RGB images are converted to CMYK as before. CMYK images are unchanged (`crates/pdf/src/tests/compression.rs`).