Add curated multi-color vector illustration case

[swernerx]

Goal

Add a curated case for a richer multi-color vector-style illustration, with overlapping regions, repeated colors, antialiasing, and a clear foreground/background structure.

Why this matters

Morphēa currently has a small real-image baseline. A more colorful illustration would test the promise that the project is not only a primitive demo, but can recover editable structure from generated or designed artwork with multiple layers and palette drift.

Example case requirements

• Use a local image with a clean illustration style, not a photo.
• Include 8-20 meaningful regions, 5-10 dominant colors, and some repeated color reuse across non-touching regions.
• Include at least one circle/ellipse-like object, at least one stroke or cut-out, and at least one organic fallback region.
• Prefer an image where expected editability can be described by regions rather than exact path coordinates.

Acceptance criteria

• Add the image metadata to the curated suite with a new family such as multi_color_vector_illustration.
• Define region-level expectations for palette grouping, simple shapes, organic fallback limits, and layer depth.
• The run report should expose whether same-color fragments were grouped or over-split.
• Add baseline snapshot evidence only after the case has a documented review status.
• Existing real-image cases remain green.

Notes

This is a good place to test whether optional MLX/SAM proposals help or hurt. The issue should still pass through the same geometry gates; AI proposals should not bypass editability checks.