[Image Modification] Add Sharp as a local image-optimization backend

Summary

add Sharp as a local backend for the existing Optimize Images command

Current behavior

Image Modification currently uses several format-specific paths:

• JPEG: NSBitmapImageRep through AppleScript
• PNG: bundled PNGOUT binary
• WebP: bundled cwebp
• AVIF: avifenc/avifdec
• SVG: SVGO

Proposal

Sharp could improve Image Modification’s common raster operations by replacing several disconnected AppleScript, SIPS and command-line pipelines with one local processing API. JPEG, PNG, WebP and AVIF images could be decoded, transformed and encoded directly without temporary JPEG or PNG round trips.
Sharp also provides explicit quality, lossless, effort, progressive-encoding, palette-quantization and metadata controls, while eliminating manually selected WebP binaries and the external libavif installation.

SVGO, Core Image, Vision, ExifTool, PDFKit, Potrace and SIPS would continue to handle features Sharp doesn't. Compression results could benfit from benchmarking because while Sharp is architecturally simple, I don't know if it would perform better on the all the various images it could be configured for.

Metadata and timestamps

Sharp strips metadata by default, so the behavior should be explicit:

• Allow embedded metadata, including EXIF/GPS, to be preserved
• Keep Strip EXIF Data as a separate intentional action
• Preserve the original filesystem modification date when replacing a file
• Document whether the macOS creation date can also be restored reliably

Selective removal of only GPS metadata could be handled separately through the extension’s existing ExifTool support.

Start by locating the existing Image Modification “Optimize Images” command and its JPEG, PNG, WebP, and AVIF processing paths. Evaluate how a local Sharp backend could fit alongside SVGO, Core Image, Vision, ExifTool, PDFKit, Potrace, and SIPS, then benchmark representative images. Done should include explicit metadata and timestamp behavior plus documented scope for features Sharp does not replace.