Add ImagePanelLayoutInvocation utility to facilitate In-Context LoRA workflows

[RyanJDick]

Summary

This PR adds a ImagePanelLayoutInvocation that makes it easy to calculate the coordinates of panels within an image grid. This utility invocation is intended to make it easier to experiment with In-Context LoRA workflows.

Example 1: Reference-Based In-Context LoRA - Reference Logo Consistency

Instructions:

1. Install this LoRA: https://huggingface.co/ali-vilab/In-Context-LoRA/blob/main/visual-identity-design.safetensors
2. Load the sample workflow: flux_icl_single_reference_image.json
3. Run.

Workflow

Sample output (cherry-picked, full grid):

Sample output (cherry-picked, cropped):

Example 2: Reference-Free In-Context LoRA - Character Consistency

Instructions:

1. Install this LoRA: https://huggingface.co/ali-vilab/In-Context-LoRA/blob/main/film-storyboard.safetensors
2. Load the sample workflow: flux_icl_reference_free.json
3. Run.

Sample output:

QA Instructions

Tested via the example workflows shown above.

Merge Plan

No special instructions.

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)