feat(nodes): add Save Image (Gallery + File Export) node

[Pfannkuchensack]

Summary

Adds a new invocation Save Image (Gallery + File Export) (save_image_to_file) that saves an image to the gallery like the standard Save Image node and additionally writes a copy to the filesystem with a customizable filename built from a prefix and suffix around the gallery UUID.

• Filename pattern: {prefix}{uuid}{suffix}.{png|jpg|webp}
• The UUID matches the gallery entry, so exported files can always be matched back to the gallery item.
• Quality input (1–100) for JPG/WEBP, ignored for PNG.
• Board and Metadata inputs behave exactly like the standard Save Image node (via WithBoard / WithMetadata mixins).
• Output directory is restricted to subfolders of the configured InvokeAI outputs folder. Absolute paths (D:/..., /etc/...) and path traversal (..) are rejected with a clear ValueError.
• Missing subdirectories are created automatically.

Example

Input	Value
prefix	hero_
suffix	_final
file_format	png
output_directory	exports/2026

Result on disk: <outputs>/exports/2026/hero_<uuid>_final.png
Gallery entry: <uuid>.png (unchanged)

Related Issues / Discussions

Closes #8372

QA Instructions

1. Start InvokeAI and open the Workflow Editor.
2. Add the new node Save Image (Gallery + File Export) (category: image).
3. Connect any image source (e.g. a generation output) to its image input.
4. Default behavior:
   • Leave output_directory, prefix, suffix empty, file_format = png.
   • Run the workflow.
   • Verify a file <uuid>.png exists in the configured outputs folder.
   • Verify the image also appears in the gallery (or on the selected board).
5. Prefix / suffix:
   • Set prefix = "test_", suffix = "_v1", run again.
   • Verify <outputs>/test_<uuid>_v1.png exists.
6. Subfolder:
   • Set output_directory = "my-exports/sub", run again.
   • Verify <outputs>/my-exports/sub/<uuid>.png exists and that the directory was created automatically.
7. JPG quality:
   • Set file_format = jpg, quality = 60, use an image with alpha.
   • Verify the file is saved as JPEG (RGB, no alpha), at a lower quality than a second run with quality = 95.
8. WEBP: Repeat with file_format = webp.
9. Security — absolute path:
   • Set output_directory = "D:/some/path" (or /tmp/foo on Linux).
   • Verify the node fails with an error mentioning “Absolute paths are not allowed”.
10. Security — path traversal:
    • Set output_directory = "../outside" or "subdir/../../outside".
    • Verify the node fails with an error about staying within the outputs folder.
11. Board / Metadata: Set a board and/or metadata and verify they are applied to the gallery entry (standard Save Image behavior).

Automated tests

20 unit tests are included in tests/app/invocations/test_save_image_to_file.py covering:

• Gallery save is invoked
• Default directory, relative subfolders, nested paths
• Prefix / suffix combinations (both, prefix only, suffix only)
• Filename uses the gallery UUID (not the input UUID)
• Absolute paths rejected (D:/, C:/, /etc, /tmp)
• Path traversal rejected (.., subdir/../../outside)
• PNG preserves alpha, JPG converts RGBA → RGB, WEBP works
• quality bounds (1–100) enforced by pydantic
• Output is a pass-through of the gallery image_dto

Run with:

uv run --extra cuda pytest tests/app/invocations/test_save_image_to_file.py -v

Merge Plan

Standard merge.

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• ❗Changes to a redux slice have a corresponding migration — N/A
• Documentation added / updated (if applicable) — N/A (node is self-documenting via rich field descriptions)
• Updated What's New copy (if doing a release after this PR) — to be decided at release time