Contract: Conversion engine

Kind: Subsystem must-guarantee (free tree)
Product should: Conversion engine PRD
How-it-works: conversion-engine.md

Role

getFileConverter(file) is the only supported router entry for choosing a Converter.
All converters implement the abstract Converter contract (convert, optimize, cancel, progress/status).
Premium adds converters and image hooks only through documented @wordpress/hooks filters.

Symbol / seam	Guarantee
`getFileConverter(file)`	Always returns a Converter; NullConverter for unknown/invalid
`requiresFileConversion(converters)`	True iff any entry is not NullConverter
`Converter` abstract	`progress` ∈ [0,1], `status`, `errorMessage`, `convert()`, `optimize()`, `cancel()`
Result object	At least `{ file }`; optional `metadata`, `reason`, `error`, `notice`
Filter `cimo.getFileConverter`	`(converter\|null, file)`; Premium returns Video/Audio/SVG converters
Filter `cimo.imageConverter.mimeTypes`	MIME list for ImageConverter
Filter `cimo.convertImage.prepare`	Async prepare before image convert (HEIC)
Filter `cimo.imageConverter.optimize`	Async smart optimize path

Cross-realm File reconstruction when instanceof File fails but shape is file-like.
Prefer original file when output grows (unless forced), on unsupported encode, or on failure.
Read runtime options from window.cimoSettings at construction time.
Free ImageConverter must not import premium modules.

Canvas math, mediabunny graphs, SVGO option bags, and resemblejs search loops are implementation behind the Converter/filter seams.