mergeTreeElements()function

mergeTreeElements(primary: T, secondary: TreeElement): T

Param	Type
`primary`	`T`	The element whose identity is preserved and whose set fields win. required
`secondary`	`TreeElement`	The element whose metadata fills any gaps in `primary`. required
`.key`	`string`	required readonly
`.type`	`tree-${string}`	required readonly

Return
`T`	A new `TreeElement` with `primary`'s identity and the merged metadata of both.

Merge two tree elements — primary keeps its identity (type, key, source); secondary contributes any
metadata primary does not already have.

title and description are taken from primary when set, otherwise from secondary — primary stays canonical
but a missing field falls back rather than disappearing.
content and children from both are concatenated (primary first).

Examples

mergeTreeElements(tsElement, mdElement) // ts identity + md prose