The labeled sites of the selected target and a whole-word text count of its name.
root is the workspace root the text scan walks. include_external only matters for callees.
The report the post-edit check reads: the labeled sites and the reach sections of target,
without the whole-word text scan and without the exclusion of a call whose argument count the
target does not accept, so a call that still passes the old count keeps its label. target
may be a symbol the index no longer holds; the report then judges the sites of its name as if
the symbol were still there, with its owner (parent_symbol_id) taken from the index.
Selects the callers target by name exactly as find_references_scoped does: the same
QueryError::SymbolNotFound (built with symbol_not_found_parts) or ambiguity error.