Merge upstream/main into revive/4330-jpeg-options

Main added DDS saving (#5993): DDS Options, and FormatChoices carrying the
Targa and DDS answers through every save path (this branch's SaveChoices
carried Targa and JPEG). Resolved by keeping main's name and making it
the one struct for all three answers.

- lib.rs: FormatChoices { tga_bits, dds, jpeg } with from_params (strict),
  from_step (lenient JPEG read of a recorded step), apply and record;
  main's separate block is folded in. Both prompts (dds_options and
  jpeg_options) are kept everywhere: save_to asks Targa, then DDS, then
  JPEG Options; save_options_open covers all four. save_in_place takes
  main's (path, choices) signature and records the plain-Save step with
  plain_save_step for JPEG plus the Targa/DDS answers (save_in_place_with
  folded into it). journal_as_plain_save relabels a parked Targa, DDS or
  JPEG prompt and keeps tgaBits/dds*/quality/jpegFormat when dropping the
  path. replay_save reads choices with from_step.
- SAVE_OPTIONS_OPEN names all four prompts; DDS Options uses it too.
- targa_options_ui: main's plain-Save step (no path) through this
  branch's write_answered_save. JPEG Options gets main's Enter-on-a-
  focused-Cancel fix.
- view_cmds Save a Copy asks Targa, DDS, then JPEG Options; write_copy
  takes FormatChoices.
- control.rs: both app.save tests (JPEG and DDS) kept.
- engine file_cmds: SaveOpts keeps jpeg_format and dds; param docs list
  both jpegFormat and ddsCompression/ddsMipmaps. CLI: both --jpeg-format
  and --dds-compression/--dds-mipmaps. codecs re-exports JpegFormat and
  DdsCompression/DdsOptions.
- docs/book: both entries kept (control-protocol app.save lists both).

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

book/src/formats/raster-formats.md

@@ -20,6 +20,7 @@ Every route that writes a document to a flat format (Save As, the CLI, MCP `doc_
 - Formats that can't embed an ICC profile (GIF, BMP, TGA, QOI, ICO, Netpbm/PFM) get RGB documents in another profile (linear light, Display P3, …) converted to sRGB through the colour engine (perceptual intent), since an untagged file is read as sRGB. OpenEXR and Radiance HDR get linear sRGB instead (linear gray for a grayscale OpenEXR), which is how they are tagged when opened.
 - TGA, as Photoshop's Targa: an RGB Targa is 24 or 32 bits per pixel. Save As and Save a Copy ask (Targa Options, starting at 32 with an alpha channel, else 24); Export As has a Resolution choice (Auto, 24 or 32 bits/pixel); scripts pass `tgaBits` (`--tga-bits` on the CLI). At 32 bits the document's alpha channel is the file's alpha when it has exactly one (spot channels don't count; with several, none is used), and the colours are written exactly, never premultiplied or cleared where the alpha is 0, so a game texture's mask and its colours both survive. Without a usable alpha channel the layers' transparency is the alpha (opaque without any). 24 bits write no alpha, compositing transparency over white. Without a choice: 32 with an alpha channel or transparency, else 24. A 32-bit Targa opens as an opaque Background with its alpha as "Alpha 1", so it round-trips. Grayscale Targas are 8-bit.
 - JPEG, as Photoshop's JPEG Options: Save As and Save a Copy ask for the Quality on Photoshop's 0–12 scale (with its Low, Medium, High and Maximum presets) and a Format Option: Baseline ("Standard"), Baseline Optimized (Huffman tables fitted to the image) or Progressive. The quality starts at the opened JPEG's own quality, else at the Export preference's JPEG quality; left there, an opened JPEG is written at exactly its own quality. Scripts pass `"quality": 0..12` and `"jpegFormat": "baseline" | "optimized" | "progressive"` (on the CLI, `--quality` on the encoder's 1–100 scale and `--jpeg-format`) and aren't asked; recorded actions replay the answer. The scale maps onto the encoder's 1–100 as `round(q / 12 × 99 + 1)`. RGB JPEGs are written 4:2:0, where Baseline Optimized keeps the standard tables for now (Gray and CMYK, written 4:4:4, get fitted ones). Matte and the file-size preview aren't offered.
+- DDS, for game and 3D textures: Save As and Save a Copy ask (DDS Options) for the compression (None, uncompressed and lossless; BC1/DXT1, whose alpha is on or off; BC2/DXT3; BC3/DXT5) and whether to generate mipmaps (the full chain down to 1×1, each level a box filter of the one above). Scripts pass `ddsCompression` (`none`, `bc1`, `bc2`, `bc3`) and `ddsMipmaps` (`--dds-compression`, `--dds-mipmaps` on the CLI). Opening one reads its top mip level.
 
 Flat TIFF and JPEG exports of composited CMYK documents convert the RGB composite back through
 the document's CMYK ICC profile (relative colorimetric with black point compensation) and embed