Function apply_to_json 

fn apply_to_json(root: &mut Value, path: &[PathSeg], action: &Action) -> bool

Applies action to the value addressed by path inside a parsed JSON document. Returns true if anything changed. Paths that do not resolve (missing key, out-of-range index, type mismatch) are silently skipped, as are regex actions on non-string values — mirroring the Lua plugin’s warn-and-continue behavior.