RFC Nested Marks

This RFC is historical. Nested marks now use the core editor engine primitives implemented in @markput/core:

• __slot__ descriptors parse nested token trees.
• ParseController owns token paths, token addresses, and parse generations.
• React and Vue render adapter-owned token shells and slot roots.
• DomController registers those structures and maps DOM selections to raw value ranges.
• useMark() returns the live MarkNode, which carries the commands.
• useMarkInfo() returns structural metadata (depth, hasNestedMarks).

Current authoring pattern:

import {useMark, useMarkInfo} from '@markput/react'

function NestedMark({children}: {children?: React.ReactNode}) {
    const mark = useMark()
    const info = useMarkInfo()

    return (
        <span data-depth={info.depth}>
            {info.hasNestedMarks ? children : (mark.slot() ?? mark.value())}
        </span>
    )
}

Parent/child traversal is intentionally not part of the public mark command API. Use token addresses for core internals and useMarkInfo() for component-level metadata.